Description：

Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

[ 题目链接 ]

注意边界：

1. 输入为0时的情况：nums = [0,3,4,0] target = 0
2. 输入为负数的情况：nums = [-1，-2，-3，-4，-5] target = -8
3. 无解时的输出（返回 NULL）

int* twoSum(int* nums, int numsSize, int target)
{
	int i, j;

	int* pos = (int*)malloc(2 * sizeof(int));

	for (i = 0; i < numsSize - 1; i++)
	{
		for (j = i + 1; j < numsSize; j++)
			if (nums[i] + nums[j] == target)
			{
				pos[0] = i;
				pos[1] = j;
				return pos;
			}
	}
	return NULL;

运行结果：