Added combination sum problem in c++

Author: sunilkumarmaurya786693

leetcode/dynamic programming/combination-sum2.cpp

@@ -0,0 +1,82 @@
+// 40. Combination Sum II
+// Medium
+
+// 7077
+
+// 175
+
+// Add to List
+
+// Share
+// Given a collection of candidate numbers (candidates) and a target number (target), find all unique combinations in candidates where the candidate numbers sum to target.
+
+// Each number in candidates may only be used once in the combination.
+
+// Note: The solution set must not contain duplicate combinations.
+
+ 
+
+// Example 1:
+
+// Input: candidates = [10,1,2,7,6,1,5], target = 8
+// Output: 
+// [
+// [1,1,6],
+// [1,2,5],
+// [1,7],
+// [2,6]
+// ]
+// Example 2:
+
+// Input: candidates = [2,5,2,1,2], target = 5
+// Output: 
+// [
+// [1,2,2],
+// [5]
+// ]
+ 
+
+// Constraints:
+
+// 1 <= candidates.length <= 100
+// 1 <= candidates[i] <= 50
+// 1 <= target <= 30
+
+class Solution {
+public:
+    vector<vector<int>>ans;
+    // map<vector<int>,bool>m;
+    void solve(vector<int>&arr, int k, int i, vector<int>&subset){
+        // for(int j=0;j<subset.size();j++)cout<<subset[j]<<" ";
+        //     cout<<k<<"\n";
+        if(k==0){
+            // if(!m[subset]){
+                ans.push_back(subset);
+                // m[subset]=true;
+            // }
+            
+            return;
+        }
+        if(k<0 || i>=arr.size())return;
+        
+        for(int j=i;j<arr.size();j++){
+            if(i!=j && arr[j]==arr[j-1])continue;
+            subset.push_back(arr[j]);
+            solve(arr,k-arr[j],j+1,subset);
+            subset.pop_back();
+        }
+
+        
+        // solve(arr,k,i+1,subset);
+        
+        
+    }
+    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
+        ans.clear();
+        // m.clear();
+        vector<int>subset;
+        sort(candidates.begin(),candidates.end());
+        solve(candidates,target,0,subset);
+        return ans;
+    }
+};