poj 2676

问题描述：

数独问题

解题要点:

回溯时要恢复回溯之前的所有状态，一开始s数组回溯时忘了清零所以结果很奇怪

代码：

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<string.h>
#include<string>
#include<cstring>

using namespace std;
const int maxn = 10;
char input[maxn][maxn];
int s[maxn][maxn];
int cubicrecord[maxn][maxn];
int linerecord[maxn][maxn];
int columnrecord[maxn][maxn];
bool success = false;

void dfs(int id);
int main()
{
	//freopen("1.txt","r",stdin);
	//freopen("2.txt","w",stdout);
	int t,i,j,part;
	scanf("%d",&t);
	while(t--)
	{
		success = false;
		memset(cubicrecord,0,sizeof(cubicrecord));
		memset(linerecord,0,sizeof(linerecord));
		memset(columnrecord,0,sizeof(columnrecord));
		memset(s,0,sizeof(s));
		memset(input,0,sizeof(input));
		for(i = 1; i < maxn;++i)
		{
			scanf("%s",input[i]);
			for(j = 1; j < maxn; ++j)
			{	
				s[i][j] = input[i][j-1] - '0';
				//scanf("%d",s[i]+j);
				part = ((i-1)/3)*3+((j-1)/3+1);
				//p[i][j] = part;
				cubicrecord[part][s[i][j]] = 1;
				linerecord[i][s[i][j]]=1;
				columnrecord[j][s[i][j]]=1;
			}
		}
		/*for(i = 1; i < maxn; ++i){
			for(j = 1; j < maxn;++j){
				printf("%d",p[i][j]);
			}
			printf("\n");
		}
		return 0;*/
		dfs(1);
		for(i = 1; i < maxn; ++i){
			for(j = 1; j < maxn; ++j){
				printf("%d",s[i][j]);
			}
			printf("\n");
		}
	}
	return 0;
}
void dfs(int id)
{
	if(success)
		return;
	int x = (id - 1) / 9 + 1;
	int y = (id - 1) % 9 + 1;
	int part =  ((x-1)/3)*3+((y-1)/3+1);
	if(id == 81)
	{
		if(s[x][y])
		{
			success = true;
			return;
		}
		for(int i = 1; i < maxn; ++i)
		{
			if((!linerecord[x][i])&&(!columnrecord[y][i])&&(!cubicrecord[part][i]))
			{
				s[9][9] = i;
				success = true;
				break;
			}
		}
		return;
	}
	
	if(s[x][y])  //这个格子已经填完了
	{
		dfs(id+1);
		if(success)
			return;
	}
	else
	{
		for(int i = 1; i < maxn; ++i)
		{
			if((!linerecord[x][i])&&(!columnrecord[y][i])&&(!cubicrecord[part][i]))
			{
				s[x][y] = i;
				linerecord[x][i] = 1;
				columnrecord[y][i] = 1;
				cubicrecord[part][i] = 1;
				dfs(id+1);
				if(success)
					break;
				linerecord[x][i] = 0;
				columnrecord[y][i] = 0;
				cubicrecord[part][i] = 0;
				s[x][y] = 0;
			}
		}
		if(success)
			return;
	}
}