Week 5 - Friday CS 121

Last time What did we talk about last time? Repetition while loops

Questions?

Project 2

Exam 1 Post Mortem

while Loop Examples

while( condition ) { statement1; statement2; … statementn; } 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 Start with the minimum and maximum of the range Find the midpoint Ask the user if the midpoint is correct If the answer is too high, go to Step 1 using the minimum and the midpoint - 1 as the new range If the answer is too low, go to Step 1 using the midpoint + 1 and the maximum as the new range 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