View Compilation Error

0_0_19140128_21366.cpp: In function 'int min_len(const char*, int, const char*, int)':
0_0_19140128_21366.cpp:12:25: error: 'strlen' was not declared in this scope
     int l1 = strlen(str1);
                         ^
0_0_19140128_21366.cpp: In function 'int main()':
0_0_19140128_21366.cpp:54:28: error: 'strlen' was not declared in this scope
         int len = strlen(s1);
                            ^
0_0_19140128_21366.cpp:70:34: error: 'strcpy' was not declared in this scope
                 strcpy(result, s2);
                                  ^
0_0_19140128_21366.cpp:71:59: error: 'strcmp' was not declared in this scope
             } else if (tmp == min_len && strcmp(s2, result) < 0) {
                                                           ^
0_0_19140128_21366.cpp:72:34: error: 'strcpy' was not declared in this scope
                 strcpy(result, s2);
                                  ^