View Compilation Error

0_0_23402396_31817.cpp: In function 'int main()':
0_0_23402396_31817.cpp:15:27: error: 'strlen' was not declared in this scope
             len=strlen(str);
                           ^
0_0_23402396_31817.cpp:28:9: error: 'else' without a previous 'if'
         else
         ^