<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:
    static bool cmp(string& a, string& b)
    {
        if (a.length() == b.length()) {
            int ret = a.compare(b);

            return ret < 0;
        }
        return a.length() > b.length();
    }
    string longestWord(vector<string>& words) {
        string ret = "";
        map<int, vector<int>> lwise;
        sort(words.begin(), words.end(), cmp);

        for (int i = 0; i < words.size(); i++) {
            if (!lwise.contains(words[i].length())) {
                lwise[words[i].length()] = {i, i};
            } else {
                lwise[words[i].length()][1] = i;
            }
        }

        for (int i = 0; i < words.size(); i++) {
            bool f = true;
            for (int j = 1, jl = words[i].length(); f && j <= jl; j++) {
                string str = words[i].substr(0, j);
                f = false;
                if (lwise.contains(str.length())) {
                    int st = lwise[str.length()][0];
                    int en = lwise[str.length()][1];

                    for (int k = st; k <= en; k++) {
                        int cmpval = str.compare(words[k]);
                        if (cmpval == 0) {
                            f = true;
                            break;
                        } else if (cmpval < 0) {
                            break;
                        }
                    }
                }
            }
            if (f) {
                ret = words[i];
                break;
            }
        }

        return ret;
    }
};
17565