View Compilation Error

0_0_20800595_27522.cpp: In function 'void search(node*, std::string, int)':
0_0_20800595_27522.cpp:82:18: error: 'strcpy' was not declared in this scope
    strcpy(ans,sum);
                  ^
0_0_20800595_27522.cpp:92:30: error: 'strlen' was not declared in this scope
  int L=strlen(tel[str[v]-'2']);
                              ^
0_0_20800595_27522.cpp: In function 'int main()':
0_0_20800595_27522.cpp:139:14: error: 'strlen' was not declared in this scope
    L=strlen(p);
              ^
0_0_20800595_27522.cpp:144:15: error: 'strcpy' was not declared in this scope
     strcpy(q,p);
               ^