/in/foo.cc: In function 'int KMPmatching(char*, char*)':
/in/foo.cc:27:14: error: 'strlen' was not declared in this scope
  n = strlen(s); m = strlen(t); next[0] = -1;
              ^
/in/foo.cc: In function 'void replace(char*, char*, char*, char*, int)':
/in/foo.cc:54:14: error: 'strlen' was not declared in this scope
  n = strlen(s); m = strlen(t); l = strlen(p);
              ^