Solo puedo mirar la solución oficial
int comp(const void* a, const void* b) {
return *(int*)a - *(int*)b;
}
int** fourSum(int* nums, int numsSize, int target, int* returnSize, int** returnColumnSizes) {
int** quadruplets = malloc(sizeof(int*) * 1001);
*returnSize = 0;
*returnColumnSizes = malloc(sizeof(int) * 1001);
if (numsSize < 4) {
return quadruplets;
}
qsort(nums, numsSize, sizeof(int), comp);
int length = numsSize;
for (int i = 0; i < length - 3; i++) {
if (i > 0 && nums[i] == nums[i - 1]) {
continue;
}
if (nums[i] + nums[i + 1] + nums[i + 2] + nums[i + 3] > target) {
break;
}
if (nums[i] + nums[length - 3] + nums[length - 2] + nums[length - 1] < target) {
continue;
}
for (int j = i + 1; j < length - 2; j++) {
if (j > i + 1 && nums[j] == nums[j - 1]) {
continue;
}
if (nums[i] + nums[j] + nums[j + 1] + nums[j + 2] > target) {
break;
}
if (nums[i] + nums[j] + nums[length - 2] + nums[length - 1] < target) {
continue;
}
int left = j + 1, right = length - 1;
while (left < right) {
int sum = nums[i] + nums[j] + nums[left] + nums[right];
if (sum == target) {
int* tmp = malloc(sizeof(int) * 4);
tmp[0] = nums[i], tmp[1] = nums[j], tmp[2] = nums[left], tmp[3] = nums[right];
(*returnColumnSizes)[(*returnSize)] = 4;
quadruplets[(*returnSize)++] = tmp;
while (left < right && nums[left] == nums[left + 1]) {
left++;
}
left++;
while (left < right && nums[right] == nums[right - 1]) {
right--;
}
right--;
} else if (sum < target) {
left++;
} else {
right--;
}
}
}
}
return quadruplets;
}