<p>You are given an array of integers <code>stones</code> where <code>stones[i]</code> is the weight of the <code>i<sup>th</sup></code> stone.</p>

<p>We are playing a game with the stones. On each turn, we choose any two stones and smash them together. Suppose the stones have weights <code>x</code> and <code>y</code> with <code>x &lt;= y</code>. The result of this smash is:</p>

<ul>
	<li>If <code>x == y</code>, both stones are destroyed, and</li>
	<li>If <code>x != y</code>, the stone of weight <code>x</code> is destroyed, and the stone of weight <code>y</code> has new weight <code>y - x</code>.</li>
</ul>

<p>At the end of the game, there is <strong>at most one</strong> stone left.</p>

<p>Return <em>the smallest possible weight of the left stone</em>. If there are no stones left, return <code>0</code>.</p>

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

<pre>
<strong>Input:</strong> stones = [2,7,4,1,8,1]
<strong>Output:</strong> 1
<strong>Explanation:</strong>
We can combine 2 and 4 to get 2, so the array converts to [2,7,1,8,1] then,
we can combine 7 and 8 to get 1, so the array converts to [2,1,1,1] then,
we can combine 2 and 1 to get 1, so the array converts to [1,1,1] then,
we can combine 1 and 1 to get 0, so the array converts to [1], then that&#39;s the optimal value.
</pre>

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

<pre>
<strong>Input:</strong> stones = [31,26,33,21,40]
<strong>Output:</strong> 5
</pre>

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

<ul>
	<li><code>1 &lt;= stones.length &lt;= 30</code></li>
	<li><code>1 &lt;= stones[i] &lt;= 100</code></li>
</ul>

class Solution {
    void func(int ind,int sum,int high,set<int>&st,vector<int>&arr){
        if(ind==(high+1)){
            st.insert(sum);
            return ;
        }
        func(ind+1 , sum+arr[ind] ,high, st , arr);
        func(ind+1 , sum-arr[ind] ,high,  st , arr);
        return ;
    }
public:
    int lastStoneWeightII(vector<int>& arr) {
        int n = arr.size() , mid = (n)/2;
        if(n==1) return arr[0];
        if(n==2) return abs(arr[1]-arr[0]);
         sort(arr.begin() , arr.end());
         set<int>a ,b;
       func(0 ,0 , mid , a , arr);
       func(mid+1 , 0 , n-1 ,b , arr);
       //cout<<a.size()<<" "<<b.size()<<endl;
      
       int ans = 1e9;
    //    for(auto it:a){
    //     int val = it;
    //     auto itr = b.upper_bound(val);
    //     if(itr!=b.end()) ans = min(ans , abs(*itr - it));
    //     if(itr!=b.begin()){
    //         itr--;
    //         ans = min(ans , abs(*itr - it));
    //     }
    //    }
    for(auto it:a){
        for(auto x:b){
            if((it+x)>=0) ans = min(ans , it+x);
        }
    }
    // for(auto it:a) cout<<it<<" ";
    // cout<<endl;
    //  for(auto it:b) cout<<it<<" ";
    //  cout<<endl;
       return ans;
    }
};
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