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Introduction to Computing Introduction to Computing Lecture Lecture 0707::
Repetition and Loop Repetition and Loop Statements (Part IStatements (Part III))
Assist.Prof.Assist.Prof.Dr. Dr. NükhetNükhet ÖZBEKÖZBEKEgeEge University University
Department of Department of Electrical & ElectronicsElectrical & Electronics Engineering Engineeringnukhetnukhet..ozbekozbek@@egeege.edu.tr.edu.tr
TopicsTopics
breakbreak statement statement continuecontinue statement statement Infinite loopsInfinite loops Nested loopsNested loops whilewhile and and forfor MacrosMacros ExampleExample
FactorizationFactorization
The The breakbreak statement statement
• Implements the "exit loop" primitiveImplements the "exit loop" primitive
• Causes flow of control to leave a loop Causes flow of control to leave a loop block (block (whilewhile or or forfor) immediately) immediately
The The continuecontinue statement statement
• Causes flow of control to start Causes flow of control to start immediately the next iteration of a immediately the next iteration of a loop block (loop block (whilewhile or or forfor))
Infinite LoopsInfinite Loops
while ( 1 )while ( 1 ) {{ ...etc...etc...etc......etc...etc...etc... }}
for ( ; 1 ; )for ( ; 1 ; ) {{ ...etc...etc...etc......etc...etc...etc... }}
for ( ; ; )for ( ; ; ) {{ ...etc...etc...etc......etc...etc...etc... }}
Use an:Use an:
if ( if ( conditioncondition ) ) {{ break;break; }}
statement to break the statement to break the looploop
Example: addpos.c Read in numbers, and Read in numbers, and
addaddonly the positive ones. only the positive ones.
QuitQuitwhen when input input is is 00
set sum to 0set sum to 0
looploop{ { input number input number if (number is negative) if (number is negative) { { begin next iteration begin next iteration } } else if ( number is zero)else if ( number is zero) { { exit loopexit loop }} add number to sum add number to sum } }
output sumoutput sum
include <stdio.h>include <stdio.h>
/****************************/****************************** Read in numbers, and add** Read in numbers, and add** ** onlyonly the positive ones. the positive ones.** Quit when ** Quit when inputinput is is 00*****************************/*****************************/
int main()int main(){{ float num, sum = 0.0;float num, sum = 0.0;
printf("sum = %f\n", sum);printf("sum = %f\n", sum); return 0;return 0;}}
Read in numbers, and Read in numbers, and addadd
only the positive ones. only the positive ones. QuitQuit
when when input input is is 00
set sum to 0set sum to 0
looploop{ { input numberinput number if (number is negative) if (number is negative) { { begin next iteration begin next iteration } } else if ( number is zero)else if ( number is zero) { { exit loopexit loop }} add number to sum add number to sum }}
output sumoutput sum
Example: addpos.c (cont)
include <stdio.h>include <stdio.h>
/****************************/****************************** Read in numbers, and add** Read in numbers, and add** only the positive ones.** only the positive ones.** Quit when ** Quit when inputinput is is 00*****************************/*****************************/
int main()int main(){{ float num, sum = 0.0;float num, sum = 0.0;
while (while (11)) {{
scanf("%f", &numscanf("%f", &num););
sum += num;sum += num; }}
printf("sum = %f\n", sum);printf("sum = %f\n", sum); return 0;return 0;}}
Read in numbers, and Read in numbers, and addadd
only the positive ones. only the positive ones. QuitQuit
when when input input is is 00
set sum to 0set sum to 0
looploop{ { input numberinput number if (number is negative) if (number is negative) { { begin next iteration begin next iteration } } else if ( number is zero)else if ( number is zero) { { exit loopexit loop } } add number to sumadd number to sum } }
output sumoutput sum
Example: addpos.c (cont)
include <stdio.h>include <stdio.h>
/****************************/****************************** Read in numbers, and add** Read in numbers, and add**** only the positive ones.only the positive ones.** Quit when ** Quit when inputinput is is 00*****************************/*****************************/
int main()int main(){{ float num, sum = 0.0;float num, sum = 0.0;
while (while (11)) {{
scanf("%f", &num)scanf("%f", &num);; if (num < 0)if (num < 0) continue;continue;
else if (num == 0)else if (num == 0) break;break;
sum += num;sum += num; }}
printf("sum = %f\n", sum);printf("sum = %f\n", sum); return 0;return 0;}}
Read in numbers, and Read in numbers, and addadd
only the positive ones. only the positive ones. QuitQuit
when when input input is is 00
set sum to 0set sum to 0
looploop{ { input number input number if (number is negative) if (number is negative) { { begin next iteration begin next iteration } } else if ( number is zero)else if ( number is zero) { { exit loopexit loop }} add number to sum add number to sum } }
output sumoutput sum
Example: addpos.c (cont)
include <stdio.h>include <stdio.h>
/****************************/****************************** Read in numbers, and add** Read in numbers, and add**** only the positive ones.only the positive ones.** Quit when ** Quit when input is 0input is 0*****************************/*****************************/
int main()int main(){{ float num, sum = 0.0;float num, sum = 0.0;
while (while (11)))) {{
scanf("%f", &numscanf("%f", &num);); if (num < 0)if (num < 0) continue;continue;
else if (num == 0)else if (num == 0) break;break;
sum += num;sum += num; }}
printf("sum = %f\n", sum);printf("sum = %f\n", sum); return 0;return 0;}}
Read in numbers, and Read in numbers, and addadd
only the positive ones. only the positive ones. QuitQuit
when when input input is is 00
set sum to 0set sum to 0
looploop{ { input number input number if (number is negative) if (number is negative) { { begin next iteration begin next iteration } } else if ( number is zero)else if ( number is zero) { { exit loopexit loop }} add number to sum add number to sum } }
output sumoutput sum
Example: addpos.c (cont)
include <stdio.h>include <stdio.h>
/****************************/****************************** Read in numbers, and add** Read in numbers, and add** only the positive ones.** only the positive ones.** Quit when ** Quit when input is 0input is 0*****************************/*****************************/
int main()int main(){{ float num, sum = 0.0;float num, sum = 0.0;
while (while (11)) {{
scanf("%f", &num)scanf("%f", &num);; if (num < 0)if (num < 0) continue;continue;
else if (num == 0)else if (num == 0) break;break;
sum += num;sum += num; }}
printf("sum = %f\n", sum);printf("sum = %f\n", sum); return 0;return 0;}}
Read in numbers, and Read in numbers, and addadd
only the positive ones. only the positive ones. QuitQuit
when when input input is is 00
set sum to 0set sum to 0
looploop{ { input number input number if (number is negative) if (number is negative) { { begin next iteration begin next iteration } } else if ( number is zero)else if ( number is zero) { { exit loopexit loop }} add number to sum add number to sum } }
output sumoutput sum
Example: addpos.c (cont)
forfor and and continuecontinue
• In the case of In the case of a a forfor statement statement,, control passes to the “update” control passes to the “update” expression.expression.
for (a = 0; a < 100; a++) { if (a%4) continue;
printf(“%d\n”,a); }
Example:
Nested Loops - Example: rect.c
Print an m by n rectangle Print an m by n rectangle ofof
asterisksasterisks
input width and heightinput width and height
for each rowfor each row{{ for each column in the current row for each column in the current row {{ print an asteriskprint an asterisk }} start next rowstart next row}}
Example: rect.c (cont) #include <stdio.h>#include <stdio.h>
//* Print an m-by-n rectangle of * Print an m-by-n rectangle of asterisksasterisks */*/
int main()int main(){{ int int i, i, jj,, m, n; m, n;
printf("\nEnter width: ");printf("\nEnter width: "); scanf("%d", &m);scanf("%d", &m); printf("\nEnter printf("\nEnter heightheight: ");: "); scanf("%d", &n);scanf("%d", &n);
return 0;return 0;}}
Print an m by n Print an m by n rectangle ofrectangle of
asterisksasterisks
input width and heightinput width and height
for for each roweach row{{ for for each columneach column in the current row in the current row {{ print an asteriskprint an asterisk }} start next rowstart next row}}
#include <stdio.h>#include <stdio.h>
//* Print an m-by-n rectangle of * Print an m-by-n rectangle of asterisksasterisks */*/
int main()int main(){{ int i, j, m, n;int i, j, m, n;
printf("\nEnter width: ");printf("\nEnter width: "); scanf("%d", &m);scanf("%d", &m); printf("\nEnter printf("\nEnter heightheight: ");: "); scanf("%d", &n);scanf("%d", &n);
for (i=0; i <for (i=0; i < nn; i++); i++) {{
}}
return 0;return 0;}}
Print an m by n Print an m by n rectangle ofrectangle of
asterisksasterisks
input width and heightinput width and height
for each rowfor each row{{ for each column in the current row for each column in the current row {{ print an asteriskprint an asterisk }} start next rowstart next row}}
Example: rect.c (cont)
#include <stdio.h>#include <stdio.h>
//* Print an m-by-n rectangle of * Print an m-by-n rectangle of asterisksasterisks */*/
int main()int main(){{ int i, j, m, n;int i, j, m, n;
printf("\nEnter width: ");printf("\nEnter width: "); scanf("%d", &m);scanf("%d", &m); printf("\nEnter printf("\nEnter heightheight: ");: "); scanf("%d", &n);scanf("%d", &n);
for (i=0; i < n; i++)for (i=0; i < n; i++) {{ for (j=0; j < for (j=0; j < mm; j++); j++) {{ }} }}
return 0;return 0;}}
Print an m by n Print an m by n rectangle ofrectangle of
asterisksasterisks
input width and heightinput width and height
for each rowfor each row{{ for each column in the current row for each column in the current row {{ print an asteriskprint an asterisk }} start next rowstart next row}}
Example: rect.c (cont)
#include <stdio.h>#include <stdio.h>
//* Print an m-by-n rectangle of * Print an m-by-n rectangle of asterisksasterisks */*/
int main()int main(){{ int i, j, m, n;int i, j, m, n;
printf("\nEnter width: ");printf("\nEnter width: "); scanf("%d", &m);scanf("%d", &m); printf("\nEnter printf("\nEnter heightheight: ");: "); scanf("%d", &n);scanf("%d", &n);
for (i=0; i < n; i++)for (i=0; i < n; i++) {{ for (j=0; j < m; j++)for (j=0; j < m; j++) {{ printf("*");printf("*"); }} }}
return 0;return 0;}}
Print an m by n Print an m by n rectangle ofrectangle of
asterisksasterisks
input width and heightinput width and height
for each rowfor each row{{ for each column in the current row for each column in the current row {{ print an asteriskprint an asterisk }} start next rowstart next row}}
Example: rect.c (cont)
#include <stdio.h>#include <stdio.h>
//* Print an m-by-n rectangle of * Print an m-by-n rectangle of asterisksasterisks */*/
int main()int main(){{ int i, j, m, n;int i, j, m, n;
printf("\nEnter width: ");printf("\nEnter width: "); scanf("%d", &m);scanf("%d", &m); printf("\nEnter printf("\nEnter heightheight: ");: "); scanf("%d", &n);scanf("%d", &n);
for (i=0; i < n; i++)for (i=0; i < n; i++) {{ for (j=0; j < m; j++)for (j=0; j < m; j++) {{ printf("*");printf("*"); }} printf("\n");printf("\n"); }}
return 0;return 0;}}
Print an m by n Print an m by n rectangle ofrectangle of
asterisksasterisks
input width and heightinput width and height
for each rowfor each row{{ for each column in the current row for each column in the current row {{ print an asteriskprint an asterisk }} start next rowstart next row}}
Example: rect.c (cont)
#include <stdio.h>#include <stdio.h>
//* Print an m-by-n rectangle of * Print an m-by-n rectangle of asterisksasterisks */*/
int main()int main(){{ int i, j, m, n;int i, j, m, n;
printf("\nEnter width: ");printf("\nEnter width: "); scanf("%d", &m);scanf("%d", &m); printf("\nEnter printf("\nEnter heightheight: ");: "); scanf("%d", &n);scanf("%d", &n);
for (i=0; i < n; i++)for (i=0; i < n; i++) {{ for (j=0; j < m; j++)for (j=0; j < m; j++) {{ printf("*");printf("*"); }} printf("\n");printf("\n"); }}
return 0;return 0;}}
Print an m by n Print an m by n rectangle ofrectangle of
asterisksasterisks
input width and heightinput width and height
for each rowfor each row{{ for each column in the current row for each column in the current row {{ print an asteriskprint an asterisk }} start next rowstart next row}}
Example: rect.c (cont)
Print an m by n Print an m by n rectangle ofrectangle of
asterisksasterisks
input width and heightinput width and height
for each rowfor each row{{ for each column in the current row for each column in the current row {{ print an asteriskprint an asterisk }} start next rowstart next row}}
#include <stdio.h>#include <stdio.h>
//* Print an m-by-n rectangle of * Print an m-by-n rectangle of asterisksasterisks */*/
int main()int main(){{ int i, j, m, n;int i, j, m, n;
printf("\nEnter width: ");printf("\nEnter width: "); scanf("%d", &m);scanf("%d", &m); printf("\nEnter printf("\nEnter heightheight: ");: "); scanf("%d", &n);scanf("%d", &n);
for (i=0; i < n; i++)for (i=0; i < n; i++) {{ for (j=0; j < m; j++)for (j=0; j < m; j++) {{ printf("*");printf("*"); }} printf("\n");printf("\n"); }}
return 0;return 0;}}
programalgorithm
Example: rect.c (cont)
#include <stdio.h>#include <stdio.h>
//* Print an m-by-n rectangle of * Print an m-by-n rectangle of asterisksasterisks */*/
int main()int main(){{ int i, j, m, n;int i, j, m, n;
printf("\nEnter width: ");printf("\nEnter width: "); scanf("%d", &m);scanf("%d", &m); printf("\nEnter printf("\nEnter heightheight: ");: "); scanf("%d", &n);scanf("%d", &n);
i = 0;i = 0; while (i < n)while (i < n) {{ for (j=0; j < m; j++)for (j=0; j < m; j++) {{ printf("*");printf("*"); }} printf("\n");printf("\n"); i++;i++; }}return 0;return 0;}}
Variation: rect2.c
PrintPrint an m by n an m by n rectangle ofrectangle of
asterisksasterisks
input width and heightinput width and height
for each rowfor each row{{ for each column in the current row for each column in the current row {{ print an asteriskprint an asterisk }} start next rowstart next row}}
#include <stdio.h>#include <stdio.h>//* Print an m-by-n rectangle of * Print an m-by-n rectangle of asterisksasterisks */*/int main()int main(){{ int i, j, m, n;int i, j, m, n;
printf("\nEnter width: ");printf("\nEnter width: "); scanf("%d", &m);scanf("%d", &m); printf("\nEnter printf("\nEnter heightheight: ");: "); scanf("%d", &n);scanf("%d", &n);
for (i=0; i < n; i++)for (i=0; i < n; i++) {{ j = 0;j = 0; while (1)while (1) {{ printf("*");printf("*"); j++;j++; if (j == m)if (j == m) break;break; }} printf("\n");printf("\n"); }} return 0;return 0;}}
PrintPrint an m by n an m by n rectangle ofrectangle of
asterisksasterisks
input width and heightinput width and height
for each rowfor each row{{ for each column in the current row for each column in the current row {{
print an asteriskprint an asterisk
}}
start next rowstart next row}}
Variation: rect3.c
#include <stdio.h>#include <stdio.h>/* Print an m-by-n rectangle of /* Print an m-by-n rectangle of
asterisks */asterisks */int main()int main(){{ int i, j, m, n;int i, j, m, n;
printf("\nEnter width: ");printf("\nEnter width: "); scanf("%d", &m);scanf("%d", &m); printf("\nEnter printf("\nEnter heightheight: ");: "); scanf("%d", &n);scanf("%d", &n);
for (i=0; i < n; i++)for (i=0; i < n; i++) {{ j = 0;j = 0; while (1)while (1) {{ printf("*");printf("*"); j++;j++; if (j == m)if (j == m) break;break; }} printf("\n");printf("\n"); }} return 0;return 0;}}
The innermost enclosing loop for this break is the while-loop
Variation: rect3.c (cont)
whilewhile and and forfor
• A A forfor loop can always be rewritten loop can always be rewritten as an equivalent as an equivalent whilewhile loop, and loop, and vice-versavice-versa
• TheThe continuecontinue statement in a statement in a forfor loop passes control to the “update” loop passes control to the “update” expression expression
ASCII (American Standard Code ASCII (American Standard Code for Information Interchange)for Information Interchange)
• Is a character encoding based on the Is a character encoding based on the English alphabet. English alphabet.
• ASCII codes represent text in ASCII codes represent text in computers, communications computers, communications equipment, and other devices that equipment, and other devices that work with textwork with text
• There are 128 characters (0-127)There are 128 characters (0-127)• First 32 (0-31) are control characters First 32 (0-31) are control characters
and are not printableand are not printable
while (1)while (1) {{ printf("Enter bounds (low high): ");printf("Enter bounds (low high): "); scanf("%d %d", &low, &high);scanf("%d %d", &low, &high);
if ((low >= 0) && (high <= 127) && (low <if ((low >= 0) && (high <= 127) && (low < high))high)) {{ break;break; }} elseelse {{ printf("Bad bounds. Try again.\n");printf("Bad bounds. Try again.\n"); }} }}
Example: asciiCheck.c
while (1)while (1) {{ printf("Enter bounds (low high): ");printf("Enter bounds (low high): "); scanf("%d %d", &low, &high);scanf("%d %d", &low, &high);
if ((low >= 0) && (high <= 127) && (low < high))if ((low >= 0) && (high <= 127) && (low < high)) {{ break;break; }} elseelse {{ printf("Bad bounds. Try again.\n");printf("Bad bounds. Try again.\n"); }} }}
Example: asciiCheck.c
Example: asciiPrintPrint out a section of the ASCII tablePrint out a section of the ASCII table
for each character from the lower bound to higher boundfor each character from the lower bound to higher bound{{ print its ascii value and ascii characterprint its ascii value and ascii character}}
for ( for ( ch = lowch = low; ; ch <= highch <= high; ; ch++ch++ ) ) {{ printf("%d: %c\n", ch, ch);printf("%d: %c\n", ch, ch); }} asciiPrint1.c
ch = lowch = low;; while ( while ( ch <= high ch <= high )) {{ printf("%d: %c\n", ch, ch);printf("%d: %c\n", ch, ch); ch++ch++;; }} asciiPrint2.c
for ( for ( ch = lowch = low; ; ch <= highch <= high; ; ch++ch++ ) ) {{ printf("%d: %c\n", ch, ch);printf("%d: %c\n", ch, ch); }}
ch = lowch = low;; while (1)while (1) {{ printf("%d: %c\n", ch, ch);printf("%d: %c\n", ch, ch); if (if (ch < highch < high)) {{ ch++;ch++; continuecontinue;; }} elseelse {{ breakbreak;; }} }} asciiPrint3.c
asciiPrint1.c
Example: asciiPrint (cont)
for ( for ( ch = lowch = low; ; ch <= highch <= high; ; ch++ch++ ) ) {{ printf("%d: %c\n", ch, ch);printf("%d: %c\n", ch, ch); }}
ch = lowch = low;; for (;;)for (;;) {{ printf("%d: %c\n", ch, ch);printf("%d: %c\n", ch, ch); ch++ch++;; if (if (ch > highch > high)) {{ breakbreak;; }} }}
asciiPrint4.c
Example: asciiPrint (cont)
asciiPrint1.c
while (1)while (1) {{ printf("Enter bounds (low high): ");printf("Enter bounds (low high): "); scanf("%d %d", &low, &high);scanf("%d %d", &low, &high);
if ((low >= MIN) && (high <= MAX)if ((low >= MIN) && (high <= MAX) && (low < high))&& (low < high)) {{ break;break; }} elseelse {{ printf("Bad bounds. Try again.\n");printf("Bad bounds. Try again.\n"); }} }}
for (ch=low; ch <= high; ch++)for (ch=low; ch <= high; ch++) {{ printf("%d: %c\n", ch, ch);printf("%d: %c\n", ch, ch); }}
return 0;return 0;}}
Example: ascii1.c
#include <stdio.h>#include <stdio.h>
/* Print a section of /* Print a section of the ASCII table */the ASCII table */
#define MIN 0#define MIN 0#define MAX 127#define MAX 127
int main()int main(){{ int low, high;int low, high; char ch;char ch;
while (1)while (1) {{ printf("Enter bounds (low high): ");printf("Enter bounds (low high): "); scanf("%d %d", &low, &high);scanf("%d %d", &low, &high);
if ((low >= MIN) && (high <= MAX)if ((low >= MIN) && (high <= MAX) && (low < high))&& (low < high)) {{ break;break; }} elseelse {{ printf("Bad bounds. Try again.\n");printf("Bad bounds. Try again.\n"); }} }}
for (ch=low; ch <= high; ch++)for (ch=low; ch <= high; ch++) {{ printf("%d: %c\n", ch, ch);printf("%d: %c\n", ch, ch); }}
return 0;return 0;}}
#include <stdio.h>#include <stdio.h>
/* Print a section of /* Print a section of the ASCII table */the ASCII table */
#define MIN 0#define MIN 0#define MAX 127#define MAX 127
int main()int main(){{ int low, high;int low, high; char ch;char ch;
Example: ascii1.c (cont)
while (1)while (1) {{ printf("Enter bounds (low high): ");printf("Enter bounds (low high): "); scanf("%d %d", &low, &high);scanf("%d %d", &low, &high);
if ((low >= if ((low >= MINMIN) && (high <= ) && (high <= MAXMAX)) && (low < high))&& (low < high)) {{ break;break; }} elseelse {{ printf("Bad bounds. Try again.\n");printf("Bad bounds. Try again.\n"); }} }}
for (ch=low; ch <= high; ch++)for (ch=low; ch <= high; ch++) {{ printf("%d: %c\n", ch, ch);printf("%d: %c\n", ch, ch); }}
return 0;return 0;}}
#include <stdio.h>#include <stdio.h>
/* Print a section of /* Print a section of the ASCII table */the ASCII table */
#define #define MINMIN 00#define #define MAXMAX 127127
int main()int main(){{ int low, high;int low, high; char ch;char ch;
Macro definition:
#define identifier tokens
All subsequent instances of identifier are replaced with its token
Example: ascii1.c (cont)
Output of Ascii1.cOutput of Ascii1.c
Enter bounds (low high): 32 126Enter bounds (low high): 32 126 32: 33:! 34:" 35:# 36:$ 37:% 38:& 39:' 40:( 41:)32: 33:! 34:" 35:# 36:$ 37:% 38:& 39:' 40:( 41:) 42:* 43:+ 44:, 45:- 46:. 47:/ 48:0 49:1 50:2 51:342:* 43:+ 44:, 45:- 46:. 47:/ 48:0 49:1 50:2 51:3 52:4 53:5 54:6 55:7 56:8 57:9 58:: 59:; 60:< 61:=52:4 53:5 54:6 55:7 56:8 57:9 58:: 59:; 60:< 61:= 62:> 63:? 64:@ 65:A 66:B 67:C 68:D 69:E 70:F 71:G62:> 63:? 64:@ 65:A 66:B 67:C 68:D 69:E 70:F 71:G 72:H 73:I 74:J 75:K 76:L 77:M 78:N 79:O 80:P 81:Q72:H 73:I 74:J 75:K 76:L 77:M 78:N 79:O 80:P 81:Q 82:R 83:S 84:T 85:U 86:V 87:W 88:X 89:Y 90:Z 91:[82:R 83:S 84:T 85:U 86:V 87:W 88:X 89:Y 90:Z 91:[ 92:\ 93:] 94:^ 95:_ 96:` 97:a 98:b 99:c 100:d 101:e92:\ 93:] 94:^ 95:_ 96:` 97:a 98:b 99:c 100:d 101:e 102:f 103:g 104:h 105:i 106:j 107:k 108:l 109:m 110:n 111:o102:f 103:g 104:h 105:i 106:j 107:k 108:l 109:m 110:n 111:o 112:p 113:q 114:r 115:s 116:t 117:u 118:v 119:w 120:x 121:y112:p 113:q 114:r 115:s 116:t 117:u 118:v 119:w 120:x 121:y 122:z 123:{ 124:| 125:} 126:~122:z 123:{ 124:| 125:} 126:~
Example : FactorizationExample : Factorization
• Write a program which prints out the Write a program which prints out the prime factoriprime factorizazation of a number (treat tion of a number (treat 2 as the first prime2 as the first prime))
• For example,For example,
on input 6,on input 6, desired desired output output is is: 2 3: 2 3
" " 24, " " 24, " " " " : : 2 2 2 32 2 2 3
" " 14, " " 14, " " " " : : 2 72 7
" " 23, " " 23, " " " " : : 23 23 ((23 23 is primeis prime))
input n
set factor to 2
Algorithm
input n
set factor to 2
while(some factor yet to try){
}
Algorithm (cont)
input n
set factor to 2
while(some factor yet to try){ if (n is divisible by factor) { output factor set n to n / factor }
}
Algorithm (cont)
input n
set factor to 2
while(some factor yet to try){ if (n is divisible by factor) { output factor set n to n / factor } else { increment factor }}
Algorithm (cont)
input n
set factor to 2
while(some factor yet to try){ if (n is divisible by factor) { output factor set n to n / factor } else { increment factor }}
while(some factor yet to try){ if (n is divisible by factor) { output factor set n to n / factor }
increment factor}
Algorithm (cont)
Why not?
#include <stdio.h>
/* Print out the prime factors of a number */
int main(){ int n, factor ;
return 0;}
Program
#include <stdio.h>
/* Print out the prime factors of a number */
int main(){ int n, factor ;
printf("\nEnter integer: ") ; scanf("%d", &n) ;
return 0;}
Program (cont)
#include <stdio.h>
/* Print out the prime factors of a number */
int main(){ int n, factor ;
printf("\nEnter integer: ") ; scanf("%d", &n) ;
printf("\nThe prime factors of %d are: ", n) ;
/* Try each possible factor in turn */
printf("\n\n"); return 0;}
Program (cont)
/* Try each possible factor in turn */
factor = 2; while ( factor <= n && n > 1 ) {
}
/* Try each possible factor in turn */
factor = 2; while ( factor <= n && n > 1 ) { if (n % factor == 0) { /* n is a multiple of factor, ** so print factor and divide n by factor */
printf(" %d", factor) ; n = n / factor ; }
}
/* Try each possible factor in turn */
factor = 2; while ( factor <= n && n > 1 ) { if (n % factor == 0) { /* n is a multiple of factor, ** so print factor and divide n by factor */
printf(" %d", factor) ; n = n / factor ; } else { /* n is not a multiple of factor; ** try next possible factor */
factor++ ; } }
/* Try each possible factor in turn */
factor = 2; while ( factor <= n && n > 1 ) { if (n % factor == 0) { /* n is a multiple of factor, ** so print factor and divide n by factor */
printf(" %d", factor) ; n = n / factor ; } else { /* n is not a multiple of factor; ** try next possible factor */
factor++ ; } }
#include <stdio.h>
/* Print out the prime factors of a number */
int main(){ int n, factor ;
printf("\nEnter integer: ") ; scanf("%d", &n) ;
printf("\nThe prime factors of %d are: ", n) ;
/* Try each possible factor in turn */
factor = 2; while ( factor <= n && n > 1 ) { if (n % factor == 0) { /* n is a multiple of factor, ** so print factor and divide n by factor. */
printf(" %d", factor) ; n = n / factor ; } else { /* n is not a multiple of factor; ** try next possible factor */
factor++ ; } } printf("\n\n"); return 0;}
factor1.c
/* Try each possible factor in turn */
factor = 2; while ( factor <= n && n > 1 ) { if (n % factor == 0) { /* n is a multiple of factor, ** so print factor and divide n by factor */
printf(" %d", factor) ; n = n / factor ; } else { /* n is not a multiple of factor; ** try next possible factor */
factor++ ; } }
Change from while-loop to for-
loop?
/* Try each possible factor in turn */
for ( factor = 2; factor <= n && n > 1 ; ) { if (n % factor == 0) { /* n is a multiple of factor, ** so print factor and divide n by factor */
printf(" %d", factor) ; n = n / factor ; } else { /* n is not a multiple of factor; ** try next possible factor */
factor++ ; } }
#include <stdio.h>
/* Print out the prime factors of a number. */
int main(){ int n, factor ;
printf("\nEnter integer: ") ; scanf("%d", &n) ;
printf("\nThe prime factors of %d are: ", n) ;
/* Try each possible factor in turn. */
for ( factor = 2; factor <= n && n > 1 ; ) { if (n % factor == 0) { /* n is a multiple of factor, ** so print factor and divide n by factor. */
printf(" %d", factor) ; n = n / factor ; } else { /* n is not a multiple of factor; ** try next possible factor. */
factor++ ; } } printf("\n\n"); return 0;}
factor2.c
