Create 3Sum.cpp

Graphs/3Sum.cpp

@@ -0,0 +1,47 @@
+class Solution {
+public:
+    vector<vector<int>> threeSum(vector<int>& arr) {
+        /*
+    for (int i = 0; i < n; i++) {
+        set<int> hashset;
+        for (int j = i + 1; j < n; j++) {
+            int third = -(arr[i] + arr[j]);
+            if (hashset.find(third) != hashset.end()) {
+                vector<int> temp = {arr[i], arr[j], third};
+                sort(temp.begin(), temp.end());
+                st.insert(temp);
+            }
+            hashset.insert(arr[j]);
+        }
+    }
+
+    
+    vector<vector<int>> ans(st.begin(), st.end());
+    return ans;
+    */
+        int n=arr.size();
+    sort(arr.begin(), arr.end());
+    set<vector<int>> st;
+    vector<int>temp;
+    int sum=0;
+        for(int i=0;i<n-2;i++){
+            int j=i+1,k=n-1;
+            while(j<k){
+                sum=arr[i]+arr[j]+arr[k];
+                if(sum==0){
+                   temp={arr[i],arr[j],arr[k]};
+                   sort(temp.begin(),temp.end());
+                   st.insert(temp);
+                }
+                if(sum>0){
+                    k--;
+                }
+                else{
+                    j++;
+                }
+            }
+        }
+        vector<vector<int>> ans(st.begin(), st.end());
+    return ans;
+    }
+};