Leetcode 配列/文字列 二重ループ

Two Sum

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

time complexity: O(n)
space complexity: O(n) The extra space required depends on the number of items stored in the hash table.