Create partition_equal_subset.cpp

Author: avidLearnerInProgress

partition_equal_subset.cpp

@@ -0,0 +1,57 @@
+class Solution {
+public:
+    
+    /*
+    best solution
+    bool cal(vector<int> nums, int sum, int i) {
+        if (i == nums.size() || sum < nums[i]) return false;
+        if (sum == nums[i]) return true;
+        
+        return cal(nums, sum - nums[i], i+1) || cal(nums, sum, i+1);
+    }
+    
+    bool canPartition(vector<int>& nums) {
+        sort(nums.rbegin(), nums.rend());
+        int sum = 0;
+        for (auto num : nums) sum += num;
+        if (sum%2) return false;
+         sum /= 2;
+        return cal(nums, sum, 0);
+    }
+    */
+    
+    bool subsetSumDP(vector<int>& nums, int sum, int n) {
+
+        //dp matrix 
+        //first col => true, first row => false
+        
+        vector<vector<bool>> dp(n + 1, vector<bool>(sum+1));
+        
+        //sum > 0 but n is 0 is not possible.. first row of dp matrix
+        for(int i=0; i<=sum; i++) dp[0][i] = false;
+        
+        //empty sum is subset => {}
+        for(int i=0; i<=n; i++) dp[i][0] = true;
+        
+        for(int i=1; i<=n; i++) {
+            for(int j=1; j<=sum; j++) {
+                
+                if(nums[i-1] <= j) //current value is less than sum => include or exclude
+                    dp[i][j] = dp[i-1][j - nums[i-1]] || dp[i-1][j];
+                
+                else
+                    dp[i][j] = dp[i-1][j]; //current value > sum; definitely exclude
+            }
+        }
+        return dp[n][sum]; 
+    }
+    
+    bool canPartition(vector<int>& nums) {
+        auto sum = 0;
+        sum = accumulate(nums.begin(), nums.end(), sum);
+        cout<<sum<<"\n";
+        if(sum % 2  != 0) return false;
+        return subsetSumDP(nums, sum/2, nums.size());
+        
+    }
+};