C Exercises: Total of two indices values equal a target

C Programming Challenges: Exercise-1 with Solution

Write a C program to get the indices of two numbers in a given array of integers. This will enable you to get the sum of two numbers equal to a specific target.

C Code:

#include <stdio.h>
#include <stdlib.h>

struct object {
    int val;
    int index;

static int compare(const void *a, const void *b)
    return ((struct object *) a)->val - ((struct object *) b)->val;

static int * two_sum(int *nums, int nums_size, int target)
    int i, j;
    struct object *objes = malloc(nums_size * sizeof(*objes));
    for (i = 0; i < nums_size; i++) {
        objes[i].val = nums[i];
        objes[i].index = i;
    qsort(objes, nums_size, sizeof(*objes), compare);
    int *results = malloc(2 * sizeof(int));
    i = 0;
    j = nums_size - 1;
    while (i < j) {
        int diff = target - objes[i].val;
        if (diff > objes[j].val) {
            while (++i < j && objes[i].val == objes[i - 1].val) {}
        } else if (diff < objes[j].val) {
            while (--j > i && objes[j].val == objes[j + 1].val) {}
        } else {
            results[0] = objes[i].index;
            results[1] = objes[j].index;
            return results;
    return NULL;

int main(void)
    int nums[] = { 4, 2, 1, 5 };
    int ctr = sizeof(nums) / sizeof(*nums);
    int target = 7;
	int i;
	printf("Original Array: ");
	for(i=0; i<ctr; i++)
        printf("%d  ", nums[i]);
    printf("\nTarget Value: %d", target);
    int *indexes = two_sum(nums, ctr, target);
    if (indexes != NULL) {
		printf("\nIndices of the two numbers whose sum equal to target value: %d", target);
        printf("\n%d %d\n", indexes[0], indexes[1]);
        printf("Not found or matched\n");

    return 0;

Sample Output:

Original Array: 4  2  1  5  
Target Value: 7
Indices of the two numbers whose sum equal to target value: 7
1 3

Pictorial Presentation:

C Programming: Get the indices of the two numbers of a given array of integers.


C Programming Flowchart: Get the indices of the two numbers of a given array of integers

C Programming Code Editor:

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C Programming: Tips of the Day

It is more efficient to use if-return-return or if-else-return?

Since the return statement terminates the execution of the current function, the two forms are equivalent (although the second one is arguably more readable than the first).

The efficiency of both forms is comparable, the underlying machine code has to perform a jump if the if condition is false anyway.

Note that Python supports a syntax that allows you to use only one return statement in your case:

return A+1 if A > B else A-1

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