C++11 置换与组合c++；逻辑错误

这是我的作业，我完成了我的代码，它确实编译了，但它没有给出正确的答案。因此，我知道有一些逻辑错误，但我无法找出是什么

Plz检查并告诉我，计算排列和组合的简单代码

#include <iostream>

using namespace std;

int factorial(int n)
{
    if (n == 0 or n == 1)
    {
        return 1;
    }
    else
    {
        return n * factorial(n - 1);
    }
}
int permutation(int a, int b)
{
    //factorial(a);

    int perm = factorial(a) / factorial(a - b);

    return perm;
}
int combination(int a, int b)
{
    int permutation(int a, int b);
    int factorial(int n);

    return permutation(a, b) / factorial(b);;
}

int main()
{
    int n;
    int r;

    cout << "Enter n: " << endl;
    cin >> n;
    cout << "Enter r: " << endl;
    cin >> r;



    int factorial(int n);
    int permutation(int n, int r);
    int combination(int n, int r);

    if (n >= r)
    {

        cout << "Permutuation: " << permutation << endl;
        cout << "Combination: " << combination << endl;

    }
    else
    {
        cout << "Invalid" << endl;
    }
    return 0;
}

---

您的代码中有许多错误。首先，不应在其他函数中重新声明“排列”和“组合”函数

编辑：事实上，这不是一个错误，但在我看来，这是一个非常糟糕的做法。您可能会意外地“隐藏”实际的函数声明，该声明已在任何调用函数之前定义

第二，你的

cout=r）{
库特
Enter n:
6
Enter r:
5
Permutuation: 00AC1375
Combination: 00AC133E

#include <iostream>
#include <iso646.h> // Need this in order to use "or" in place of "||"
using namespace std;

int factorial(int n)
{
    if (n == 0 or n == 1) {
        return 1;
    }
    else {
        return n * factorial(n - 1);
    }
}

int permutation(int a, int b)
{
    //factorial(a);
    int perm = factorial(a) / factorial(a - b);
    return perm;
}

int combination(int a, int b)
{
//  int permutation(int a, int b); // You don't need to redeclare function inside another one ...
//  int factorial(int n);
    return permutation(a, b) / factorial(b);;
}

int main()
{
    int n, r;
    cout << "Enter n: " << endl;
    cin >> n;
    cout << "Enter r: " << endl;
    cin >> r;
//  int factorial(int n);
    int p = permutation(n, r); // This is how to call your functions ...
    int c = combination(n, r); // and assign their returns to values.
    if (n >= r) {
        cout << "Permutuation: " << p << endl; // Output the values ...
        cout << "Combination: " << c << endl;  // ...from the functions
    }
    else {
        cout << "Invalid" << endl;
    }
    return 0;
}