1. Two Sum

class Solution {
    public int[] twoSum(int[] nums, int target) {
         int[] result = new int[2];
            Map<Integer, Integer> map = new HashMap<Integer, Integer>();
            for (int i = 0; i < nums.length; i++) {
                if (map.containsKey(target - nums[i])) {
                    result[1] = i ;
                    result[0] = map.get(target - nums[i]);
                    return result;
                }
                map.put(nums[i], i);
            }
            return result;
    }
}

class Solution {
public:
    
    vector<int> twoSum(vector<int>& nums, int target) {
    
        map<int,int> themap;
        vector<int> result;

        for(int i=0;i<=nums.size()-1;i++)
        {
            if(themap.find(target-nums[i])!=themap.end())
            {
                result.push_back(themap.find(target-nums[i])->second);
                result.push_back(i);
                return result;
            }

            themap.insert(make_pair(nums[i],i));
        }

        return result;
    }
    
};