View Compilation Error

0_0_30663760_18959.cpp: In function 'int main()':
0_0_30663760_18959.cpp:42:34: error: 'strlen' was not declared in this scope
             lens[i] = strlen(s[i]);
                                  ^
0_0_30663760_18959.cpp:44:30: error: 'strlen' was not declared in this scope
         int len = strlen(s[0]);
                              ^