leetcode - 1. Two Sum

哈希问题

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        vector<int> ret;
        int n=nums.size(),x;
        unordered_map<int,int>hash;
        unordered_map<int,int>::iterator it;
        for(int i=0;i<n;++i)
        {
            x=nums[i];
            it=hash.find(x);
            if(it!=hash.end())
            {
                ret.push_back(it->second);
                ret.push_back(i);
                return ret;
            }else{
                hash[target-x]=i;
            }
        }
        return ret;
    }
};