AP Computer Science A Unit 4 Iteration | Amherst College

University:
Amherst College
Course:
COSC 111 | Introduction to Computer Science I
Academic year:

2022
Views:

462

Pages:

2
Author:

Shyanne Johnson

Unit 4: Iteration While Loops: The while statement allows a code block to repeat as long as a condition is true. while (expression) { // one or more statements } If expression is true the code will run, after it runs expression is checked again and if true will run, this continues until expression is false. If expression is false the first time the body of code will not run. When writing a while loop make sure that the condition becomes false or else the code will execute infinitely. For Loops: A for loop uses a variable to count the iterations of a loop. for (initialization; expression; increment) { // statements } When the loop is first encountered, the initialization statement is executed. Then expression is evaluated. If it is true, the loop body is executed. After execution, increment is executed, and expression is evaluated again. This continues until expression is false, at which point the loop is done. Developing Algorithms and Using Strings: Loops can be used to process Strings; the indexOf and substring methods are a few ways strings can be processed. for (int i = 0; i < myStr.length() – k + 1; i++) { String subs = myStr.substring(i, i + k); // do something with subs } Here “i” is used to keep track of the index in a string. In each iteration a substring of length k is retrieved starting at index i. Nested Iteration: A nested loop is when a loop is put in the body of another loop. Nested loops are commonly used in more complex string and array algorithms. for (int x = 5; x >= 1; x--) { for (int y = 0; y < x; y++) { System.out.print(y + " "); } System.out.println(); } Informal Code Analysis: What makes a good algorithm: -correctness, does the code work as intended -efficiency, as little unnecessary or overcomplicated code as possible -easily understandable by others/ will someone be able to understand what the code is supposed to do