View Compilation Error

0_0_14928884_24802.cpp: In function 'int main()':
0_0_14928884_24802.cpp:18:37: error: 'strlen' was not declared in this scope
             for (i = 1; i < strlen(s); i++)
                                     ^
0_0_14928884_24802.cpp:26:30: error: 'strlen' was not declared in this scope
             if (i == strlen(s))
                              ^