1 class Solution { 2 public: 3     vector<string> restoreIpAddresses( string s ) { 4         string ip; 5         ProcessSub( ip, 0, s ); 6         return address; 7     } 8 private: 9     void ProcessSub( string ip, int step, string str ) {10         if( step == 4 ) { address.push_back( ip ); return; }11         int sLen = str.length();12         if( sLen < 4-step || sLen > 3*(4-step) ) { return; }13         for( int i = max( 1, sLen-3*(3-step) ); i <= min( 3, sLen-(3-step) ); ++i ) {14             string subStr = str.substr( 0, i );15             if( IsLegal( subStr ) ) {16                 if( !ip.empty() ) { subStr = ip + "." + subStr; }17                 ProcessSub( subStr, step+1, str.substr( i ) );18             }19         }20     }21     bool IsLegal( const string& str ) {22         if( str.length() == 1 ) { return true; }23         if( str[0] == ‘0‘ ) { return false; }24         int value = http://www.mamicode.com/0;25         for( size_t i = 0; i != str.length(); ++i ) {26             value = http://www.mamicode.com/10 * value + str[i] - ‘0‘;27         }28         if( value > 255 ) {  return false; }29         return true;30     }31     vector<string> address;32 };