线性代数，行列式求值。

第一次发代码，来试试水~~

#include<iostream>
#include<vector>
using namespace std;

using Vector = vector<vector<int>>;

class D
{
protected:

	int num;
	int level;
	Vector arr;

public:
	D():num(1), level(1) {}
	int(*x)[5] = new int[120][5];
	void init()
	{
		cout << "请输入行列式长度：";
		cin >> num;
		arr.resize(num);
		system("cls");
		int temp;
		for (int i = 0; i < num; i++)
		{
			for (int j = 0; j < num; j++)
			{
				cin >> temp;
				arr[i].push_back(temp);
			}
		}
	}

	int getD()
	{
		int result = 0;
		for (int i = num; i > 1; i--)
		{
			level *= i;
		}
		int* y = new int[num]();
		vector<int> m;
		for (int i = 0; i < num; i++)
		{
			*(y + i) = i;
			m.push_back(i);
		}

		getX(m, 0, 0, level);

		for (int i = 0; i < level; i++)
		{
			result += multip(arr, x[i]);
		}
		return result;
	}
	int ab(int a[])//判断正负
	{
		int data = 0;
		for (int i = 0; i < num; i++)
		{
			for (int j = i + 1; j < num; j++)
			{
				if (a[i] > a[j])
					data++;
			}
		}
		if (data % 2 == 0)
			return 1;
		else
			return -1;
	}

	int multip(Vector vec, int a[])
	{
		int data = 1;
		for (int i = 0; i < num; i++)
		{
			data *= vec[i][a[i]];
		}
		data *= ab(a);
		return data;
	}
	void getX(std::vector<int> vec, int a, int b, int size)//求列标的所有排列组合
	{
		int size_t = 1;
		if (num - b != 0)
			size_t = size / (num - b);
		for (int i = 0; i < num - b; i++)
		{
			vector<int> temp = vec;
			for (int j = 0; j < size_t; j++)
			{
				x[a + j][b] = temp[i];
			}
			temp.erase(temp.begin() + i);
			getX(temp, a, b + 1, size_t);
			a += size_t;
		}
	}
};


int main()
{
	D d;
	d.init();
	cout << "D=" << d.getD() << endl;

	system("pause");
	return 0;
}