View Compilation Error

0_0_19325488_898.cpp: In function 'int main()':
0_0_19325488_898.cpp:17:37: error: 'strlen' was not declared in this scope
         for(int j = 0 ; j < strlen(s) ; j++ )
                                     ^
0_0_19325488_898.cpp:24:41: error: 'strlen' was not declared in this scope
             if(cnt == 0) ans = (strlen(s)+1)/2;
                                         ^
0_0_19325488_898.cpp:27:28: error: 'strlen' was not declared in this scope
                 if(strlen(s) - (posC[cnt-1] - posC[0]) <=2 ) {flag = 1 ;}
                            ^