View Compilation Error

0_0_20681796_32053.cpp: In function 'int main()':
0_0_20681796_32053.cpp:52:29: error: 'strlen' was not declared in this scope
             if(strlen(str[i]) > len) {  
                             ^
0_0_20681796_32053.cpp:59:44: error: 'strlen' was not declared in this scope
             end = end * len + strlen(str[i]);  
                                            ^