<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) {
        int n = strs.size();
        int last = 0;
        if(strs.size() == 1) return strs[0];
        string res = find_common_prefix(strs[0], strs[1]);
        if( res == "") return res;
        for(int i=1; i<n; i++){
            res = find_common_prefix(res, strs[i]);
            if(res == "") return res;
        } 
        return res;
    }
    string find_common_prefix(string s1, string s2)
    {
        int n1 = s1.length();
        int n2 = s2.length();
        string output = "";
        if(n1 == 0 || n2 == 0) return output;
        int l = min(n1, n2);
        for(int i=0; i<l; i++){
            if(s1[i] != s2[i]) break;
            else{
                output += s1[i];
            }
        }
        return output;
    }
};
12000