01.md

暴力法

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        for(int i = 0; i < nums.size(); i ++ ) {
            int r = target - nums[i];
            for(int j = i + 1; j < nums.size(); j ++ ) {
                if(nums[j] == r) return {i, j};
            }
        }
        return {};
    }
};

哈希表法

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        unordered_map<int, int> map;
        for (int i = 0; i < nums.size(); i ++ ) {
            int r = target - nums[i];
            if (map.count(r)) return {map[r], i};
            map[nums[i]] = i;
        }
        return {};
    }
};