<p>Given an integer array <code>nums</code>, return <code>true</code> <em>if you can partition the array into two subsets such that the sum of the elements in both subsets is equal or </em><code>false</code><em> otherwise</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,5,11,5]
<strong>Output:</strong> true
<strong>Explanation:</strong> The array can be partitioned as [1, 5, 5] and [11].
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,3,5]
<strong>Output:</strong> false
<strong>Explanation:</strong> The array cannot be partitioned into equal sum subsets.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 200</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 100</code></li>
</ul>

class Solution {
public:
    bool canPartition(vector<int>& nums) {
        int s=0;
        for(int i=0; i<nums.size(); i++)
            s += nums[i];
        if(s%2) return false;

        vector<vector<int>>dp(nums.size() + 1, vector<int>(s + 1, 0));
        return helper(nums, 0, s/2, dp);
    }

    bool helper(vector<int>& nums, int i, int x, vector<vector<int>> &dp) {
        if (i>=nums.size() || x<0) {
            return false;
        }

        if (dp[i][x] != 0) {
            return (dp[i][x] == 2);
        }

        if (x==0) {
            dp[i][x] = 2;
            return true;
        }
        
        bool ans = helper(nums, i+1, x-nums[i], dp) || helper(nums, i+1, x, dp);
        if (ans) dp[i][x] = 2;
        else dp[i][x] = 1;
        return ans;
    }
};
185356