combo.cpp: In function 'std::string guess_sequence(int)':
combo.cpp:20:3: error: 'vector' was not declared in this scope
20 | vector <char> dd = {'A', 'B', 'X', 'Y'};
| ^~~~~~
combo.cpp:2:1: note: 'std::vector' is defined in header '<vector>'; did you forget to '#include <vector>'?
1 | #include "combo.h"
+++ |+#include <vector>
2 | using namespace std;
combo.cpp:20:11: error: expected primary-expression before 'char'
20 | vector <char> dd = {'A', 'B', 'X', 'Y'};
| ^~~~
combo.cpp:22:9: error: 'dd' was not declared in this scope
22 | if (dd[i] == x) {
| ^~
combo.cpp:29:28: error: 'dd' was not declared in this scope
29 | string f1 = ret; f1 += dd[0]; f1 += dd[0];
| ^~
combo.cpp:44:26: error: 'dd' was not declared in this scope
44 | string u = ret; u += dd[i];
| ^~