Basic While vs For vs Do Function Timer

#include <stdio.h>
#include <time.h>

void while_loop(int target) {
    int i = 0;
    while (i < target) {
        printf("%d\n", i);
        i++;
    }
}

void for_loop(int target) {
    for (int i = 0; i < target; i++) {
        printf("%d\n", i);
    }
}

void do_loop(int target) {
    int i = 0;
    do {
        printf("%d\n", i);
        i++;
    } while (i < target);
}

int main() {
    int target = 0;
    printf("Enter the target amount: ");
    scanf("%d", &target);

    printf("What function do you want to measure?\n\n");
    printf("1. While loop\n");
    printf("2. For loop\n");
    printf("3. Do loop\n");
    printf("4. Exit\n\n");

    int choice = 0;
    printf("Enter your choice: ");
    scanf("%d", &choice);

    clock_t start = NULL;
    switch (choice) {
        case 1:
            start = clock();
            while_loop(target);
            break;
        case 2:
            start = clock();
            for_loop(target);
            break;
        case 3:
            start = clock();
            do_loop(target);
            break;
        case 4:
            break;
        default:
            printf("Invalid choice\n");
            break;
    }

    if (start != NULL) {
        clock_t end = clock();
        double time_spent = (double)(end - start) / CLOCKS_PER_SEC;
        printf("Time spent: %f\n", time_spent);
    } else {
        printf("No time spent\n");
    }

    return 0;
}