Return inside loops in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of return inside a for loop

What is the output of this C program?

C

#include <stdio.h>

int test() {
    for (int i = 0; i < 5; i++) {
        if (i == 2) {
            return i;
        }
    }
    return -1;
}

int main() {
    printf("%d\n", test());
    return 0;
}

A -1

B 0

C 4

D 2

💡 Hint

The function returns as soon as i equals 2 inside the loop.

The loop runs from i=0 to i=4. When i reaches 2, the return statement exits the function immediately with value 2.

❓ Predict Output

intermediate

Return inside while loop behavior

What will this program print?

C

#include <stdio.h>

int count_down(int n) {
    while (n > 0) {
        if (n == 3) {
            return n;
        }
        n--;
    }
    return 0;
}

int main() {
    printf("%d\n", count_down(5));
    return 0;
}

A 0

B 3

C 1

D 5

💡 Hint

The function returns when n equals 3 during the countdown.

The while loop decreases n from 5 down to 1. When n is 3, the function returns 3 immediately.

🔧 Debug

advanced

Why does this function return early?

Consider this function. Why does it return 0 instead of 10?

C

#include <stdio.h>

int sum_until_five() {
    int sum = 0;
    for (int i = 1; i <= 10; i++) {
        if (i == 5) {
            return 0;
        }
        sum += i;
    }
    return sum;
}

int main() {
    printf("%d\n", sum_until_five());
    return 0;
}

A Because the loop never runs

B Because sum is reset to 0 when i is 5

C Because the return 0 inside the loop stops the function when i is 5

D Because sum is returned before the loop starts

💡 Hint

Look at the return statement inside the loop and when it triggers.

The function returns 0 immediately when i reaches 5, so it never sums beyond 4.

❓ Predict Output

advanced

Return inside nested loops

What does this program print?

C

#include <stdio.h>

int nested_loop() {
    for (int i = 1; i <= 3; i++) {
        for (int j = 1; j <= 3; j++) {
            if (i * j == 4) {
                return i + j;
            }
        }
    }
    return 0;
}

int main() {
    printf("%d\n", nested_loop());
    return 0;
}

A 5

B 6

C 4

D 0

💡 Hint

Find the first pair (i,j) where i*j equals 4 and return their sum.

The nested loops check i from 1 to 3 and j from 1 to 3. The first time i*j == 4 is when i=2 and j=2, so it returns 2+2=4.

❓ Predict Output

expert

Return inside loop with break and continue

What is the output of this program?

C

#include <stdio.h>

int tricky() {
    for (int i = 0; i < 5; i++) {
        if (i == 2) {
            continue;
        }
        if (i == 3) {
            break;
        }
        if (i == 1) {
            return i;
        }
    }
    return -1;
}

int main() {
    printf("%d\n", tricky());
    return 0;
}

A 1

B -1

C 0

D 3

💡 Hint

Remember that return exits the function immediately, continue skips to next loop iteration, and break exits the loop.

When i=0, no condition triggers. When i=1, return i exits function with 1. So output is 1.