Added solution

Author: avidLearnerInProgress

two_sum_ii.cpp

@@ -0,0 +1,26 @@
+class Solution {
+public:
+    vector<int> twoSum(vector<int>& numbers, int target) {
+        unordered_map<int, int> mp;
+        vector<int> solution(2, 0);
+        
+        //store difference as first element of map and index as second element of map
+        for(int i=0; i<numbers.size(); i++){
+            int difference = target - numbers[i];
+            auto it = mp.find(difference);
+            
+            //elements not in map
+            if(it != mp.end()){
+                if(mp[difference] < i){
+                solution[0] = mp[difference] + 1;
+                solution[1] = i + 1;
+                return solution;
+                }
+            }
+            else
+                mp[numbers[i]] = i;
+
+        }
+        return vector<int>(2, 0);
+    }
+};