I wanted to use a queue with a Problem structure variable as a type, so I declared a variable, but there was an error, so I'm uploading a question.
For example, if you have a structureProblem{};
I want to use a variable called queueQ; but I used an undefined format.
Display error C2027.
What's interesting is that there's an error when you do a queue, but there's no error
Below is the source code.
using namespace std;
structure Problem;//structure type forward declaration
queue<problem>Q;//where error occurs
If I write English in vector<problem>Bank;//<>, I can't see it on the screen, so I wrote it in Korean.
struct Problem {
intarr[5] = {3,3,0,0,0};//Initial state;
int brr[5];
Problem() {//Generator
for (int i = 0; i < 5; i++) { brr[i] = arr[i]; }
Problem a = *this; Bank.push_back(a);
}
voidoriginal() {//keep the original
for (int i = 0; i < 5; i++) { arr[i] = brr[i];}
}
void clear() {//move to pre-migration state
for (int i = 0; i < 5; i++) { brr[i] = arr[i]; }
}
};
int main() { Problem mc;
cout << mc.arr[0] << mc.arr[1] << mc.arr[2] << mc.arr[3] << mc.arr[4] << endl; return 0; }
struct prototype queue vector forward-declaration
The reason for the C2027 error is because Queue<Problem>Q; is not defined when the variable is generated.
A forward declaration only tells you that there is a type of this name, but it does not tell you the definition of that type.
Therefore, the two variables queue<Problem> Q; and vector<Problem> Bank; must be defined in Problem and .
However, if Therefore, the definitions of If you want to leave two variables Q and Bank are lowered below the Problem<:/code> definition, Problem::Problem() will depend on BankQ and Bank should be lowered, and the definitions of Problem::Problem() should also be lowered.#include <iostream>
#include <vector>
#include <queue>
using namespace std;
struct Problem
{
intarr[5] = {3, 3, 0, 0, 0}; //Initial state;
int brr[5];
Problem();
void original()
{ //Keep original
for (int i = 0; i < 5; i++)
{
arr[i] = brr[i];
}
}
void clear()
{ //Move to pre-migration state
for (int i = 0; i < 5; i++)
{
brr[i] = arr[i];
}
}
};
queue<Problem> Q;
vector<Problem> Bank;
Problem::Problem()
{ //Generator
for (int i = 0; i < 5; i++)
{
brr[i] = arr[i];
}
Problem a = *this;
Bank.push_back(a);
}
int main()
{
Problem mc;
cout << mc.arr[0] << mc.arr[1] << mc.arr[2] << mc.arr[3] << mc.arr[4] << endl;
return 0;
}
Q and Bank on top, replace the two containers std::vector and std:queue with a non-procode template.
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