Merge pull request #40 from vipu18/patch-2

Implement subset sum problem using dynamic programming

Author: admirerr

CPP/dynamic-programming/count_subsets_with_sum_k.cpp

@@ -0,0 +1,45 @@
+#include <iostream>
+#include <vector>
+using namespace std;
+
+// Paste your Solution class here (choose one implementation)
+class Solution {
+    int mod = 1000000007;
+public:
+    int perfectSum(vector<int>& arr, int k) {
+        int n = arr.size();
+        vector<int>prev(k+1, 0);
+        vector<int>curr(k+1, 0);
+        curr[0] = 1;
+        prev[0] = 1;
+        if(arr[0]<=k){
+            prev[arr[0]] = 1;
+        }
+        for(int i = 1; i<n; i++){                
+            for(int tar = 1; tar<=k; tar++){
+                int notTaken = prev[tar];
+                int take = 0;
+                if(arr[i]<=tar){
+                    take = prev[tar-arr[i]] % mod;
+                }
+                curr[tar] = (notTaken+take) % mod;
+            }
+            prev = curr;
+        }
+        return prev[k];
+    }
+};
+
+int main() {
+    int n, k;
+    cout << "Enter number of elements and target sum: ";
+    cin >> n >> k;
+    vector<int> arr(n);
+    cout << "Enter array elements: ";
+    for(int i=0; i<n; ++i) cin >> arr[i];
+
+    Solution sol;
+    int result = sol.perfectSum(arr, k);
+    cout << "Number of subsets with sum " << k << ": " << result << endl;
+    return 0;
+}