<p>Given an integer array <code>queries</code> and a <strong>positive</strong> integer <code>intLength</code>, return <em>an array</em> <code>answer</code> <em>where</em> <code>answer[i]</code> <em>is either the </em><code>queries[i]<sup>th</sup></code> <em>smallest <strong>positive palindrome</strong> of length</em> <code>intLength</code> <em>or</em> <code>-1</code><em> if no such palindrome exists</em>.</p>

<p>A <strong>palindrome</strong> is a number that reads the same backwards and forwards. Palindromes cannot have leading zeros.</p>

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

<pre>
<strong>Input:</strong> queries = [1,2,3,4,5,90], intLength = 3
<strong>Output:</strong> [101,111,121,131,141,999]
<strong>Explanation:</strong>
The first few palindromes of length 3 are:
101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, ...
The 90<sup>th</sup> palindrome of length 3 is 999.
</pre>

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

<pre>
<strong>Input:</strong> queries = [2,4,6], intLength = 4
<strong>Output:</strong> [1111,1331,1551]
<strong>Explanation:</strong>
The first six palindromes of length 4 are:
1001, 1111, 1221, 1331, 1441, and 1551.
</pre>

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

<ul>
	<li><code>1 &lt;= queries.length &lt;= 5 * 10<sup>4</sup></code></li>
	<li><code>1 &lt;= queries[i] &lt;= 10<sup>9</sup></code></li>
	<li><code>1 &lt;= intLength&nbsp;&lt;= 15</code></li>
</ul>

class Solution {
public:

    long long getMaxi(int m){
        long long ret=9;
        for(int i=0;i<m;i++){
            ret=ret*10+9;
        }
        return ret;
    }


    long long getPalin(int x,int l){
        string s=to_string(x);
        int m=s.length();
        for(int i=m;i<l;i++)
            s+="1";
        int n=s.length();
        for(int i=0;i<m;i++)
            s[n-i-1]=s[i];
        return stoll(s);
    }

    vector<long long> kthPalindrome(vector<int>& queries, int l) {
        int n=queries.size();
        vector<long long> ans(n);
        int m=(l+1)/2;
        long long first=pow(10,m-1);
        int maxi=getMaxi(m-1)-first+1;
        // cout<<getMaxi(m-1)<<endl;
        int x;
        for(int i=0;i<n;i++) {
            x=queries[i];
            if(x>maxi){
                ans[i]=-1;
                continue;
            }
            x=first+x-1;
            // cout<<x<<endl;
            ans[i]=getPalin(x,l);
        }
        return ans;
    }
};
55000