leetcode-1-two sum

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.

Example:
Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
UPDATE (2016/2/13):
The return format had been changed to zero-based indices. Please read the above updated description carefully.

在给定数组中找到两个数的和为目标值，求出对应的两个值的坐标。

对原数组进行哈希存储，值对应坐标即可，然后查询差值是否在哈希表中。

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        vector<int> res;
        map<int,int> m;
        if(nums.empty()) return res;
        for(int i = 0 ; i < nums.size(); i++)
        {
            int rest = target-nums[i];
            if(m.find(rest)!=m.end()){
                res.push_back(m[rest]);
                res.push_back(i);
                break;
            }else{
                m[nums[i]]=i;
            }
        }
        return res;
    }
};