<p>Given an array of strings <code>words</code> representing an English Dictionary, return <em>the longest word in</em> <code>words</code> <em>that can be built one character at a time by other words in</em> <code>words</code>.</p>

<p>If there is more than one possible answer, return the longest word with the smallest lexicographical order. If there is no answer, return the empty string.</p>

<p>Note that the word should be built from left to right with each additional character being added to the end of a previous word.&nbsp;</p>

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

<pre>
<strong>Input:</strong> words = [&quot;w&quot;,&quot;wo&quot;,&quot;wor&quot;,&quot;worl&quot;,&quot;world&quot;]
<strong>Output:</strong> &quot;world&quot;
<strong>Explanation:</strong> The word &quot;world&quot; can be built one character at a time by &quot;w&quot;, &quot;wo&quot;, &quot;wor&quot;, and &quot;worl&quot;.
</pre>

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

<pre>
<strong>Input:</strong> words = [&quot;a&quot;,&quot;banana&quot;,&quot;app&quot;,&quot;appl&quot;,&quot;ap&quot;,&quot;apply&quot;,&quot;apple&quot;]
<strong>Output:</strong> &quot;apple&quot;
<strong>Explanation:</strong> Both &quot;apply&quot; and &quot;apple&quot; can be built from other words in the dictionary. However, &quot;apple&quot; is lexicographically smaller than &quot;apply&quot;.
</pre>

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

<ul>
	<li><code>1 &lt;= words.length &lt;= 1000</code></li>
	<li><code>1 &lt;= words[i].length &lt;= 30</code></li>
	<li><code>words[i]</code> consists of lowercase English letters.</li>
</ul>

class Solution {
public:
    string longestWord(vector<string>& arr) {
        string ans="";
        int count=0;
       sort(arr.begin(),arr.end());
       vector<int>dp(arr.size()+1,0);
    //    for(int i=0;i<arr.size();i++)cout<<arr[i]<<" ";
    //    cout<<endl;
       for(int i=0;i<arr.size();i++){
        int len = arr[i].size();
        if(len==1){dp[i]=1; if(count==0){count=1;ans=arr[i];} continue;}
        // cout<<arr[i]<<" :";
        int trig=0;
        for(int j=i-1;j>=0;j--){
            // cout<<arr[j]<<" ";
            // for(int t=0;t<dp.size();t++)cout<<dp[t]<<" ";
            // cout<<endl;
            if(dp[j]==-1)continue;
            int second =arr[j].size();
            if(abs(second-len)==1 && second<len){
                string s=arr[i];
                s.pop_back();
                if(s==arr[j]){
                    dp[i]=max(dp[i],1+dp[j]);
                    if(dp[i]>count){
                        count=dp[i];
                        ans=arr[i];
                    }
                    trig=1;
                    break;
                }
            }
        }
        if(trig==0)dp[i]=-1;
       }
       return ans;
    }
};
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