View Compilation Error

0_0_33097674_13878.cpp: In function 'bool contain(char*, char)':
0_0_33097674_13878.cpp:7:29: error: 'strlen' was not declared in this scope
  for (int i = 0;i < strlen(a);i++) {
                             ^
0_0_33097674_13878.cpp: In function 'int main()':
0_0_33097674_13878.cpp:30:32: error: 'strlen' was not declared in this scope
  for (int i = 0;i < strlen(test);i++) {
                                ^