View Compilation Error

0_0_35258336_7670.cpp: In function 'bool KMP(int)':
0_0_35258336_7670.cpp:28:35: error: 'strlen' was not declared in this scope
         int len2 = strlen(s[i] + 1);
                                   ^
0_0_35258336_7670.cpp: In function 'int main()':
0_0_35258336_7670.cpp:54:34: error: 'strlen' was not declared in this scope
         int len = strlen(s[1] + 1);
                                  ^
0_0_35258336_7670.cpp:63:40: error: 'strcpy' was not declared in this scope
                 strcpy(s2 + 1, s[1] + l);
                                        ^
0_0_35258336_7670.cpp:71:51: error: 'strcmp' was not declared in this scope
                         if (strcmp(s2 + 1, res + 1) < 0)
                                                   ^