1. Two Sum - cocoder39/coco39_LC GitHub Wiki

class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
            int complement = target - nums[i];
            if (map.containsKey(complement)) {
                return new int[] { map.get(complement), i };
            }
            map.put(nums[i], i);
        }
        return null;
    }
}

vector<int> twoSum(vector<int>& nums, int target) {
        vector<int> res;
        unordered_map<int, int> map; //map[val] = idx;
        for (int i = 0; i < nums.size(); i++) {
            int pair = target - nums[i];
            if (map.find(pair) != map.end()) {
                res = {map[pair], i};
                return res;
            }
            map[nums[i]] = i;
        }
        return res;
    }