暴力破解法：

    1. /**
    2.  * Note: The returned array must be malloced, assume caller calls free().
    3.  */
    4. int* twoSum(int* nums, int numsSize, int target, int* returnSize){
    5.     int i, j;
    6.     for (i = 0; i < numsSize - 1; ++i) {
    7.         for (j = i + 1;j < numsSize; ++j) {
    8.             if ((nums[i] + nums[j]) == target) {
    9.                 int* result = (int*)malloc(2 * sizeof(int));
    10.                 result[0] = i;
    11.                 result[1] = j;
    12.                 *returnSize = 2;
    13.                 return result;
    14.             }
    15.         }
    16.     }
    18.     return NULL;
    19. }

    结果：

    通过 92 ms 6 MB C

    下一步看看能否优化