Leetcode每日一题-两数之和

1、两数之和

暴力解

class Solution {
public:
    vector twoSum(vector& nums, int target) {
        int i,j;
        for(i=0;i

倒推法

class Solution {
public:
    vector twoSum(vector& nums, int target) {
        int i,j;
        for(i=1;i

哈希法

注意vector和unordered_map的用法

class Solution {
public:
    vector twoSum(vector& nums, int target) {
        vectorres;
        unordered_map hash;
        for(int i=0;i({hash[another],i});
                return res;
            }
            hash[nums[i]]=i;
        }
        return res;
    }
};