poj 3752 字母旋转游戏 回溯

又水了道题，罪过..

#include <stdio.h>
#include <string.h>

int n,m;
char board[100][100];

int dfs(int x,int y,int num,int d)
{
	int i,row,col,dir[4][2]={0,1,1,0,0,-1,-1,0};
	if (num==n*m)return 1;
	for (i=d;;i++)
	{
		row=x+dir[i%4][0];
		col=y+dir[i%4][1];
		if(row>=0&&col>=0&&row<n&&col<m&&board[row][col]=='.')
		{
			board[row][col]='A'+num%26;
			if(dfs(row,col,num+1,i%4))return 1;
		}
	}
	return 0;
}

int main()
{
	int i,j;
	while (scanf("%d%d",&n,&m)!=EOF)
	{
		memset(board,'.',sizeof(board));
		board[0][0]='A';
		dfs(0,0,1,0);
		for (i=0;i<n;i++)
		{
			for (j=0;j<m;j++)
				printf("   %c",board[i][j]);
			printf("\n");
		}
	}
	return 0;
}