leetcode 刷题记录

尚未佩妥剑，转眼便江湖，记录一下自己写过的题
1.array
(1)twoSum
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].

代码

遍历数组，将遍历过的vector存到map里面，键值为order，再去find，返回order。

using namespace std;
#include 
#include 
#include 
class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        map <int,int> hashmap;
        vector <int> result;
        for (int i = 0; i < nums.size(); i++) {
            int toFind = target - nums[i];
            if (hashmap.find(toFind) != hashmap.end()) {
                result.push_back(hashmap[toFind]);
                result.push_back(i+1);
                return result;
            }
            hashmap[nums[i]] = i;
        }
    }
};
//如果没有找到，返回null, vector的size为0，亲测。时间复杂度为o[n]