POJ 2676 sudoku

　　数独问题。给定其中的几个数，找出其他符合规则的数。保证所给数据合法。典型的DFS。 又是1A真爽。

　　首先用三个数组标记每列每行每个九宫格出现过的数字。然后DFS寻找可能的状态。跑了400+ms。

#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <cstring>
#include <cstdio>

using namespace std;

int sudoku[10][10];

bool MarkDfs,hr[10][10],hc[10][10],hs[10][10];

int JudgeS(int i,int j)
{
    if(1 <= i && i <= 3 && 1 <= j && j <= 3)
        return 1;
    if(1 <= i && i <= 3 && 4 <= j && j <= 6)
        return 2;
    if(1 <= i && i <= 3 && 7 <= j && j <= 9)
        return 3;
    if(4 <= i && i <= 6 && 1 <= j && j <= 3)
        return 4;
    if(4 <= i && i <= 6 && 4 <= j && j <= 6)
        return 5;
    if(4 <= i && i <= 6 && 7 <= j && j <= 9)
        return 6;
    if(7 <= i && i <= 9 && 1 <= j && j <= 3)
        return 7;
    if(7 <= i && i <= 9 && 4 <= j && j <= 6)
        return 8;
    if(7 <= i && i <= 9 && 7 <= j && j <= 9)
        return 9;
}

void dfs(int r,int c)
{
    if(MarkDfs == false)
        return;
    int i,j,k;
    for(i = r;i <= 9; ++i)
    {
        for(j = (i == r ? c : 1);j <= 9; ++j)
        {
            if(sudoku[i][j] == 0)
            {
                for(k = 1;k <= 9; ++k)
                {
                    if(hr[i][k] == false && hc[j][k] == false && hs[JudgeS(i,j)][k] == false)
                    {
                        hr[i][k] = true;
                        hc[j][k] = true;
                        hs[JudgeS(i,j)][k] = true;
                        sudoku[i][j] = k;
                        dfs(i,j);
                        if(MarkDfs)
                        {
                            sudoku[i][j] = 0;
                            hr[i][k] = false;
                            hc[j][k] = false;
                            hs[JudgeS(i,j)][k] = false;
                        }
                    }
                }
                return ;
            }
        }
    }
    MarkDfs = false;
}

int main()
{
    int T;
    int i,j;

    scanf("%d",&T);

    while(T--)
    {
        memset(hr,false,sizeof(hr));
        memset(hc,false,sizeof(hc));
        memset(hs,false,sizeof(hs));

        MarkDfs = true;

        for(i = 1;i <= 9; ++i)
        {
            for(j = 1;j <= 9; ++j)
                scanf("%1d",&sudoku[i][j]);
        }

        for(i = 1; i <= 9; ++i)
        {
            for(j = 1;j <= 9; ++j)
            {
                hr[i][sudoku[i][j]] = true;
                hc[j][sudoku[i][j]] = true;
                hs[JudgeS(i,j)][sudoku[i][j]] = true;
            }
        }

        dfs(1,1);

        for(i = 1;i <= 9; ++i)
        {
            for(j = 1;j <= 9; ++j)
            {
                printf("%d",sudoku[i][j]);
            }
            printf("
");
        }

    }
    return 0;
}