Create target-sum.cpp

Author: kamyu104

C++/target-sum.cpp

@@ -0,0 +1,28 @@
+// Time:  O(n * S)
+// Space: O(S)
+
+class Solution {
+public:
+    int findTargetSumWays(vector<int>& nums, int S) {
+        // sum(P) - sum(N) = S
+        //       <=>
+        // 2 * sum(P) = S + sum(nums)
+        int sum = accumulate(nums.begin(), nums.end(), 0);
+        if (sum < S || (S + sum) % 2) {
+            return 0;
+        }
+        return subsetSum(nums, (S + sum) / 2); 
+    }   
+
+private:
+    int subsetSum(vector<int>& nums, int S) {
+        vector<int> dp(S + 1);
+        dp[0] = 1;
+        for (const auto& n : nums) {
+            for (int i = S; i >= n; --i) {
+                dp[i] += dp[i - n];
+            }
+        }
+        return dp.back();
+    }
+};