<p>Given an integer array <code>nums</code> and an integer <code>k</code>, return <code>true</code> if it is possible to divide this array into <code>k</code> non-empty subsets whose sums are all equal.</p>

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

<pre>
<strong>Input:</strong> nums = [4,3,2,3,5,2,1], k = 4
<strong>Output:</strong> true
<strong>Explanation:</strong> It is possible to divide it into 4 subsets (5), (1, 4), (2,3), (2,3) with equal sums.
</pre>

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

<pre>
<strong>Input:</strong> nums = [1,2,3,4], k = 3
<strong>Output:</strong> false
</pre>

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

<ul>
	<li><code>1 &lt;= k &lt;= nums.length &lt;= 16</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 10<sup>4</sup></code></li>
	<li>The frequency of each element is in the range <code>[1, 4]</code>.</li>
</ul>

class Solution {
public:
    int n;
    int subsetSum;
    bool solve(int currSum, int mask, vector<int>& nums, int k, vector<int>& dp) {
        if (k == 0) return (mask == ((1 << n) - 1));
        if (currSum == subsetSum) return solve(0, mask, nums, k-1, dp);
        if (dp[mask] != -1) return dp[mask];
        bool ans = false;
        for (int i = 0; i < n; i++) {
            if (mask & (1 << i)) continue;
            if (currSum + nums[i] <= subsetSum) {
                int newMask = mask | (1 << i);
                if (solve(currSum + nums[i], newMask, nums, k, dp)) {
                    ans = true;
                    break;
                }
                //ans = solve(currSum + nums[i], newMask, nums, k, dp);
                //newMask = newMask ^ (1 << i);
            }
        }
        return dp[mask] = ans;
    }
    bool canPartitionKSubsets(vector<int>& nums, int k) {
        n = nums.size();
        int sum = accumulate(nums.begin(), nums.end(), 0);
        if (sum % k) return false;
        subsetSum = sum / k;
        vector<int> dp((1 << n) - 1, -1);
        return solve(0, 0, nums, k, dp);
    }
};
23540