<p>Write a function to find the longest common prefix string amongst an array of strings.</p>

<p>If there is no common prefix, return an empty string <code>&quot;&quot;</code>.</p>

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

<pre>
<strong>Input:</strong> strs = [&quot;flower&quot;,&quot;flow&quot;,&quot;flight&quot;]
<strong>Output:</strong> &quot;fl&quot;
</pre>

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

<pre>
<strong>Input:</strong> strs = [&quot;dog&quot;,&quot;racecar&quot;,&quot;car&quot;]
<strong>Output:</strong> &quot;&quot;
<strong>Explanation:</strong> There is no common prefix among the input strings.
</pre>

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

<ul>
	<li><code>1 &lt;= strs.length &lt;= 200</code></li>
	<li><code>0 &lt;= strs[i].length &lt;= 200</code></li>
	<li><code>strs[i]</code> consists of only lowercase English letters.</li>
</ul>

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if (strs.empty()) return "";

        int minLen = strs[0].length();
        for (const string& str : strs) {
            minLen = min(minLen, (int)str.length());
        }

        unordered_map<int, unordered_map<char, int>> charMap;

        for (int i = 0; i < minLen; ++i) {
            for (const string& str : strs) {
                charMap[i][str[i]]++;
            }
        }

        string result;
        for (int i = 0; i < minLen; ++i) {
            if (charMap[i].size() == 1 && charMap[i].begin()->second == strs.size()) {
                result += charMap[i].begin()->first;
            } else {
                break;
            }
        }

        return result;
    }
};
12400