CS 121Week 5 - Friday

Last time

What did we talk about last time? Repetitionwhile loops

Questions?

Project 2

while Loop Examples

Anatomy of a while loop

while( condition ){

statement1;statement2;…statementn;

}

A whole bunch of

statements

Guessing game

Let’s say that you wanted to write a program to guess a number that a person had come up with

The number is between 1 and 100 Every time the computer guesses a

number, the person enters: H if the number is too high L if the number is too low F if the number was found

Guessing game algorithm

1. Start with the minimum and maximum of the range

2. Find the midpoint3. Ask the user if the midpoint is correct4. If the answer is too high, go to Step 1

using the minimum and the midpoint - 1 as the new range

5. If the answer is too low, go to Step 1 using the midpoint + 1 and the maximum as the new range

6. If the midpoint is correct, you’re done!

Nested loops

Just as with if-statements, it’s possible to nest loops

A repetitive task can be done inside of another repetitive task

Be careful! You can make the computer do a lot of work

Triangular numbers

Triangular numbers are 1, 3, 6, 10, … 1 = 1 3 = 1 + 2 6 = 1 + 2 + 3 10 + 1 + 2 + 3 + 4

Let’s write a program that expresses the nth triangular number by printing 1 on the first line, 1 and 2 on the second line, 1, 2, and 3 on the third line, and so on

Lab 5

Upcoming

Next time…

for loops More loop examples

Reminders

Keep reading Chapter 5 Keep working on Project 2