Longest Common Prefix

 1 class Solution {
 2 public:
 3     string longestCommonPrefix( vector<string> &strs ) {
 4         if( strs.empty() ) { return string(""); }
 5         int start = -1;
 6         while( ++start < strs[0].length() ) {
 7             for( int i = (int)strs.size()-1; i > 0; --i ) {
 8                 if( strs[i][start] != strs[0][start] ) { return strs[0].substr( 0, start ); }
 9             }
10         }
11         return strs[0].substr( 0, start );
12     }
13 };