解数独

解数独

#include<stdio.h>
#include<stdbool.h>
char grid[] =
{
	5,3,0,0,7,0,0,0,0,
	6,0,0,1,9,5,0,0,0,
	0,9,8,0,0,0,0,6,0,
	8,0,0,0,6,0,0,0,3,
	4,0,0,8,0,3,0,0,1,
	7,0,0,0,2,0,0,0,6,
	0,6,0,0,0,0,2,8,0,
	0,0,0,4,1,9,0,0,5,
	0,0,0,0,8,0,0,7,9

};
#define length 60
int flag[length] = { 0 };
int index = 0;

bool isValid(int row, int col, char val, char grid[]) {
	for (int j = 0; j < 9; j++) {
		if (grid[row * 9 + j] == val) {
			return false;
		}
	}
	for (int i = 0; i < 9; i++) {
		if (grid[i * 9 + col] == val) {
			return false;
		}
	}

	int startRow = (row / 3) * 3;
	int startCol = (col / 3) * 3;
	for (int i = startRow; i < startRow + 3; i++) { // 判断9方格里是否重复
		for (int j = startCol; j < startCol + 3; j++) {
			if (grid[i * 9 + j] == val) {
				return false;
			}
		}
	}
	return true;
}
bool backtracking(char grid[]) {
	for (int i = 0; i < 9; i++) {        // 遍历行
		for (int j = 0; j < 9; j++) { // 遍历列
			if (grid[i * 9 + j] != 0) continue;
			for (char k = 1; k <= 9; k++) {     // (i, j) 这个位置放k是否合适
				if (isValid(i, j, k, grid)) {
					grid[i * 9 + j] = k;                // 放置k
					if (backtracking(grid))
					{
						flag[index] = k;
						index++;
						return true; // 如果找到合适一组立刻返回
					}

					grid[i * 9 + j] = 0;              // 回溯，撤销k
				}
			}
			return false;                           // 9个数都试完了，都不行，那么就返回false
		}
	}
	return true; // 遍历完没有返回false，说明找到了合适棋盘位置了
}

int main() {

	backtracking(grid);
	printf("\n");
	//输出数独表
	for (int i = 0; i < 9; i++) {
		for (int j = 0; j < 9; j++) {
			printf("%d", grid[i * 9 + j]);
		}
		printf("\n");
	}
	//输出要填的数字
	for (int i = length - 1; i >= 0; i--) {
		printf("%d", flag[i]);
	}
	return 0;
}