洛谷P1784 数独进阶解法

#include<iostream>
#include<array>

using namespace std;
array<array<int, 9>, 9>a;


int sudofind(int m, int n, array<int, 9>& b)
{
	array<int, 10>c;
	b.fill(0);
	c.fill(0);
	for (int i = 0; i < 9; i++)
	{
		c[a[i][n]]++;
		c[a[m][i]]++;
	}
	for (int i = m - m % 3; i <= m + 2 - m % 3; i++)
		for (int j = n - n % 3; j <= n + 2 - n % 3; j++)
			c[a[i][j]]++;
	int k = 0;
	for (int i = 1; i < 10; i++)
		if (0 == c[i])
		{
			b[k] = i;
			k++;
		}
	return k;
}

bool sudoku(int m, int n)
{
	if (8 == m && 8 == n)
	{
		if (0 != a[m][n])
			return true;
		else
		{
			array<int, 9>b;
			sudofind(m, n, b);
			if (0 != b[0])
			{
				a[m][n] = b[0];
				return true;
			}
			else
				return false;
		}
	}
	else if (0 == a[m][n])
	{
		array<int, 9>b;
		int end = sudofind(m, n, b);
		if (0 == b[0])
			return false;
		else
		{
			for (int k = 0; k < end; k++)
			{
				a[m][n] = b[k];
				if (8 != n)
				{
					if (true == sudoku(m, n + 1))
						return true;
				}
				else if (8 != m)
					if (true == sudoku(m + 1, 0))
						return true;
				a[m][n] = 0;
			}
			return false;
		}
	}
	else if (8 != n)
	{
		if (true == sudoku(m, n + 1))
			return true;
	}
	else if (8 != m)
		if (true == sudoku(m + 1, 0))
			return true;
}

int main()
{
	for (int i = 0; i < 9; i++)
		for (int j = 0; j < 9; j++)
			cin >> a[i][j];
	if (true == sudoku(0, 0))
		for (int i = 0; i < 9; i++)
		{
			for (int j = 0; j < 9; j++)
				cout << a[i][j] << ' ';
			cout << endl;
		}
	return 0;
}