Create _15.cpp

Author: Anshul1507

cpp/_15.cpp

@@ -0,0 +1,40 @@
+class Solution {
+public:
+    vector<vector<int>> threeSum(vector<int>& nums) {
+        sort(nums.begin(),nums.end());
+        
+        vector<vector<int>> v;
+        
+        if(nums.size()<3){
+            //if vector nums has less than 3 elements, impossible to distribute into 3 element set -> return 0.
+            return v;
+        }
+        
+        for(int i=0;i<nums.size();i++){
+            
+            if(i>0 and nums[i]==nums[i-1]){
+                //same elements dont have to be taken.
+                continue;
+            }
+            
+            int l = i+1, r = nums.size()-1;
+            //Using 2-pointer concept
+            while(l<r){
+                int sum = nums[i] + nums[l] + nums[r];
+                if(sum>0){
+                    r--;
+                }else if(sum<0){
+                    l++;
+                }else{
+                    v.push_back(vector<int> {nums[i],nums[l],nums[r]});
+                    while(l<r and nums[l]==nums[l+1]) l++;
+                    while(l<r and nums[r]==nums[r-1]) r--;
+                    l++; r--;
+                }
+            }
+            
+        }
+        
+        return v;
+    }
+};