// 15. 3Sum #include "leetcode.h" /* * given an integer array 'nums', return all the triplets '[nums[i], nums[j], * nums[k]]' such that 'i != j', 'i != k', 'j != k', and 'nums[i] + nums[j] + * nums[k] == 0'. notice that the solution set must not contain duplicate * triplets */ int cmp(const void *a, const void *b) { return *((int *)a) - *((int *)b); } int **threeSum(int *nums, int numsSize, int *returnSize, int **returnColumnSizes) { qsort(nums, numsSize, sizeof(int), cmp); (*returnSize) = 0; (*returnColumnSizes) = (int *)malloc(sizeof(int) * numsSize * numsSize); int **ans = (int **)malloc(numsSize * numsSize * sizeof(int *)); for (int i = 0; i < numsSize - 2; i++) if (!i || nums[i] != nums[i - 1]) { int l = i + 1, r = numsSize - 1; while (l < r) { if (nums[i] + nums[l] + nums[r] < 0) l++; else if (nums[i] + nums[l] + nums[r] > 0) r--; else { ans[(*returnSize)] = (int *)malloc(3 * sizeof(int)); (*returnColumnSizes)[(*returnSize)] = 3; ans[(*returnSize)][0] = nums[i]; ans[(*returnSize)][1] = nums[l]; ans[(*returnSize)][2] = nums[r]; (*returnSize)++; l++; while (l < r && nums[l] == nums[l - 1]) l++; } } } return ans; } int main() { int n1[] = {-1, 0, 1, 2, -1, -4}, rs1, *rcs1; int n2[] = {0, 1, 1}, rs2, *rcs2; int n3[] = {0, 0, 0}, rs3, *rcs3; int **ts1 = threeSum(n1, ARRAY_SIZE(n1), &rs1, &rcs1); int **ts2 = threeSum(n2, ARRAY_SIZE(n2), &rs2, &rcs2); int **ts3 = threeSum(n3, ARRAY_SIZE(n3), &rs3, &rcs3); for (int i = 0; i < rs1; i++) { for (int j = 0; j < *rcs1; j++) printf("%d ", ts1[i][j]); // expect: [[-1,-1,2],[-1,0,1]] printf("\n"); } printf("\n"); for (int i = 0; i < rs2; i++) { for (int j = 0; j < *rcs2; j++) printf("%d ", ts2[i][j]); // expect: null printf("\n"); } printf("\n"); for (int i = 0; i < rs3; i++) { for (int j = 0; j < *rcs3; j++) printf("%d ", ts3[i][j]); // expect: [[0,0,0]] printf("\n"); } printf("\n"); for (int i = 0; i < rs1; i++) free(ts1[i]); free(ts1); for (int i = 0; i < rs2; i++) free(ts2[i]); free(ts2); for (int i = 0; i < rs3; i++) free(ts3[i]); free(ts3); }