4.4: Nested Iteration

Learning Objective: Represent nested iteration processes

Essential Knowledge:

Nested iteration is when an iteration statement appears inside the body of another iteration statement
The inner loop must complete all of its iterations before the outer loop can continue.

Before uncommenting the code, guess what the output will look like:

(write your guess here)

public class NestedLoops{

    public static void main(String[] args){

        // for (int outer = 1; outer < 5; outer++){

        //     for (int inner = 1; inner < 3; inner++){
                
        //         System.out.print(inner + " ");
        //     }

        //     System.out.println();

        // } 

    }
}

NestedLoops.main(null)

What will the output of the code above be if we switch the loop headers (the stuff inside of the for loop)?

(Write your guess here)

After making a prediction actually switch the loop headers for yourself. What do you notice about the output compared to the output before the change?

4.5: Informal Code Analysis

Essential Knowledge:

A statement exectution count indicates the number of times a statement is executed by the program

for (int outer = 0; outer < 3; outer++){
    for (int inner = 0; inner < 4; inner++){
        // statement #1
    }
}

In the code above, how many times will the inner loop execute when outer = 0? 4

In the code above, how many times will the inner loop execute when outer = 1? 4

In the code above, how many times will the inner loop execute when outer = 2? 4

In the code above, how many times will the inner loop execute in total? 12

for (int outer = 5; outer > 0; outer--){
    for (int inner = 0; inner < outer; inner++){
        // statement #1
    }
}

In the code above, how many times will the inner loop execute when outer = 5? 5

In the code above, how many times will the inner loop execute when outer = 4? 4

In the code above, how many times will the inner loop execute when outer = 3? 3

In the code above, how many times will the inner loop execute in total? 15

int k = 0;
while (k < 5){
    int x = (int)(Math.random()*6) + 1;
    while (x != 6){
        //statement #1
        x = (int)(Math.random()*6) + 1;
    }
    k++;
}

In the code above, how many times will the statement #1 execute? We can’t tell, since it’s based on rng

for (int k = 0; k < 135; k++){
    if (k % 5 == 0){ // Statement #1
        System.out.print(k); // Statement #2
    }
}

In the code above, how many times will the statement #1 execute? 135

In the code above, how many times will the statement #2 execute? 27

Rewrite the code above to be more effecient based on execution count.

for (int k = 0; k < 135; k+=5){
    System.out.print(k); // Statement #2
}

4.4 and 4.5 • 7 min read

Description

4.4: Nested Iteration

4.5: Informal Code Analysis