CppSolutionTwoSum.cpp

Two Sum/twoSum.cpp

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+// Question Link :- https://leetcode.com/problems/two-sum/
+
+// Below is Solution
+
+//1st Approach
+// Time Complexity :- O(n^2)
+
+class Solution {
+public:
+    vector<int> twoSum(vector<int>& nums, int target) {
+       vector<int> v;
+        for(int i=0;i<nums.size()-1;i++){
+            for(int j=i+1;j<nums.size();j++){
+                if(nums[i]+nums[j]==target){
+                    v.push_back(i);
+                    v.push_back(j);
+                }
+            }
+        }
+        return v;
+    }
+};
+
+//OR
+
+//2nd Approach
+//HashMaps
+//Time Complexity-O(n) 
+
+class Solution {
+public:
+    vector<int> twoSum(vector<int>& nums, int target) {
+     unordered_map<int,int> m;
+        for(int i=0;i<nums.size();i++){
+            int x=nums[i];
+            int y=target-x;
+            if(m.find(y)!=m.end()){
+                return {i,m[y]};
+            }
+            m[nums[i]]=i;
+        }
+       return {-1,-1}; 
+    }
+};