From 67681aa751bb0e3183c27d0f04f0514e02b60582 Mon Sep 17 00:00:00 2001
From: Swastika Gupta <64654203+Swastyy@users.noreply.github.com>
Date: Mon, 28 Jun 2021 17:20:08 +0530
Subject: [PATCH] Create subset_sum.cpp

---
 backtracking/subset_sum.cpp | 91 +++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 backtracking/subset_sum.cpp

diff --git a/backtracking/subset_sum.cpp b/backtracking/subset_sum.cpp
new file mode 100644
index 000000000..74668a91c
--- /dev/null
+++ b/backtracking/subset_sum.cpp
@@ -0,0 +1,91 @@
+/**
+ * @file
+ * @brief Program to Count number of subsets 
+ *
+ * @details Subset problem (https://en.wikipedia.org/wiki/Subset_sum_problem)
+ * @author [Swastika Gupta](https://github.com/swastyy)
+ */
+ 
+#include <cassert>    /// for assert
+#include <iostream>   /// for io operations
+#include <vector>     /// for std::vector
+ 
+/**
+ * @namespace backtracking
+ * @brief subset sum algorithm
+ */
+namespace backtracking {
+/**
+ * @namespace Subsets
+ * @brief Functions for counting subsets in a given array with a given sum
+ */
+namespace Subsets {
+/**
+ * @brief The main function implements count of subsets
+ * @param sum is the required sum of any subset
+ * @param in_arr is the input array
+ * @returns count of the number of subsets with required sum
+ */
+
+std::uint64_t subset_sum(int sum, std::vector<int>& in_arr) {
+    int nelement = in_arr.size();	//number of subset element
+	int count_of_subset = 0;
+
+	for(int i=0; i < (1 << (nelement)); i++){
+		std::vector<int> subset;
+		for(int j=0;j<nelement;j++){
+			if (i & (1<<j)){
+				subset.push_back(in_arr[j]);
+			}
+		}
+		int check=0;
+		for(int k=0;k<subset.size();k++){
+			check+=subset[k];
+		}
+		if(check==sum)
+			count_of_subset++;
+	}
+	return count_of_subset;
+}
+}  // namespace Subsets
+}  // namespace backtracking
+
+/**
+ * @brief Test implementations
+ * @returns void
+ */
+static void test() {
+    // Test 1
+    std::cout << "1st test ";
+    std::vector<int> array1 = {-7,-3,-2,5,8}; // input array
+    assert(backtracking::Subsets::subset_sum(0,array1)==2); // first argument in subset_sum function is the required sum and second is the input array
+    std::cout << "passed" << std::endl;
+
+    // Test 2
+    std::cout << "2nd test ";
+    std::vector<int> array2 = {1, 2, 3, 3}; // input array
+    assert(backtracking::Subsets::subset_sum(6,array2)==3); // first argument in subset_sum function is the required sum and second is the input array
+    std::cout << "passed" << std::endl;
+
+    // Test 3
+    std::cout << "3rd test ";
+    std::vector<int> array3 = {1, 1, 1, 1}; // input array
+    assert(backtracking::Subsets::subset_sum(1,array3)==4); // first argument in subset_sum function is the required sum and second is the input array
+    std::cout << "passed" << std::endl;
+
+    // Test 4
+    std::cout << "4th test ";
+    std::vector<int> array4 = { 3, 3, 3, 3 }; // input array
+    assert(backtracking::Subsets::subset_sum(6,array4)==6); // first argument in subset_sum function is the required sum and second is the input array
+    std::cout << "passed" << std::endl;
+}
+
+
+/**
+ * @brief Main function
+ * @returns 0 on exit
+ */
+int main() {
+    test();  // execute the test
+    return 0;
+}