leetcode之2sum

题目：

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.

解答：

直接用hash即可，在C++中就是map

一开始看错了，看成找这两个数了，如果是这样就直接排序，

class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
map<int, int> m;
int size = nums.size();
int left;
for (int i = 0; i < size; ++i)
{
left = target - nums[i];
auto itr = m.find(left);
if (itr != m.end())
return{ i, itr->second };
m[nums[i]] = i;
}
}
};