<p>You are given an integer array <code>matchsticks</code> where <code>matchsticks[i]</code> is the length of the <code>i<sup>th</sup></code> matchstick. You want to use <strong>all the matchsticks</strong> to make one square. You <strong>should not break</strong> any stick, but you can link them up, and each matchstick must be used <strong>exactly one time</strong>.</p>

<p>Return <code>true</code> if you can make this square and <code>false</code> otherwise.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/04/09/matchsticks1-grid.jpg" style="width: 253px; height: 253px;" />
<pre>
<strong>Input:</strong> matchsticks = [1,1,2,2,2]
<strong>Output:</strong> true
<strong>Explanation:</strong> You can form a square with length 2, one side of the square came two sticks with length 1.
</pre>

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

<pre>
<strong>Input:</strong> matchsticks = [3,3,3,3,4]
<strong>Output:</strong> false
<strong>Explanation:</strong> You cannot find a way to form a square with all the matchsticks.
</pre>

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

<ul>
	<li><code>1 &lt;= matchsticks.length &lt;= 15</code></li>
	<li><code>1 &lt;= matchsticks[i] &lt;= 10<sup>8</sup></code></li>
</ul>

class Solution {
public:
    bool solve(vector<int> nums,vector<bool>& visited,int currsum,int idx,int subsetsum,int k){
        if(k==0)return true;
        if(currsum>subsetsum)return false;
        if(currsum==subsetsum){
            return solve(nums,visited,0,0,subsetsum,k-1);
        }
        for(int i=idx;i<nums.size();i++){
            if(visited[i])continue;
            visited[i] = true;
            if(solve(nums,visited,currsum+nums[i],i+1,subsetsum,k))return true;
            visited[i] = false;
            if(currsum==0)break;
        }
        return false;
    }
    bool makesquare(vector<int>& nums) {
        int k=4;
        int n = nums.size();
        if(k > n)return false;
        int sum=0;
        for(auto n : nums)
            sum += n;
       if (nums.size() < k || sum % k) return false;
        int subsetsum = sum/k;
        vector<bool> v(n,false);
        sort(nums.begin(), nums.end(), greater<int>());
        if(nums[0]>subsetsum)
            return false;

        return solve(nums,v,0,0,subsetsum,k);
    }
    
};
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