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

            seen[arr[i]] = i;
        }

        return {};
    }
};

https://leetcode.com/problems/two-sum/

https://takeuforward.org/data-structure/two-sum-check-if-a-pair-with-given-sum-exists-in-array/