poj 2676 Sudoku （dfs）

最新推荐文章于 2020-02-25 10:33:58 发布

cillyb

最新推荐文章于 2020-02-25 10:33:58 发布

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分类专栏：搜索文章标签：算法 poj 搜索

本文链接：https://blog.youkuaiyun.com/CillyB/article/details/53044637

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本文介绍了一种通过深度优先搜索解决数独问题的算法实现。该算法能够在较短时间内找到数独的有效解决方案，并讨论了正向搜索与反向搜索在效率上的显著差异。

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解数独..暴搜即可

一开始傻逼的以为没必要把格子还原为0，wa了半天还坚信这不用还原...长记性了。。

还有这题正搜和反搜时间差好多，正搜要400ms反搜只需16ms....

代码：

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
char tpic[15][15];
int pic[15][15], book_row[10][10], book_col[10][10], book_cel[5][5][10];
bool ok;

void dfs(int x, int y)
{
    if(ok) return ;
    if(y == 9) x++, y = 0;
    if(x == 9) { ok = 1; return ; }
    if(pic[x][y]) dfs(x, y+1);
    else
    {
        for(int i = 1; i <= 9; i++)
        {
            if(!book_row[x][i] && !book_col[y][i] && !book_cel[x/3][y/3][i])
            {
                pic[x][y] = i;
                book_row[x][i] = book_col[y][i] = book_cel[x/3][y/3][i] = 1;
                dfs(x, y+1);
                if(ok) return ;
                pic[x][y] = book_row[x][i] = book_col[y][i] = book_cel[x/3][y/3][i] = 0;
            }
        }
    }
}

int main(void)
{
    //freopen("in.txt", "r", stdin);
    int t;
    cin >> t;
    while(t--)
    {
        ok = 0;
        memset(book_row, 0, sizeof(book_row));
        memset(book_col, 0, sizeof(book_col));
        memset(book_cel, 0, sizeof(book_cel));
        for(int i = 0; i < 9; i++)
            for(int j = 0; j < 9; j++)
            {
                scanf(" %c", &tpic[i][j]);
                int val = tpic[i][j]-48;
                pic[i][j] = val;
                if(val) book_row[i][val] = book_col[j][val] = book_cel[i/3][j/3][val] = 1;
            }
        dfs(0, 0);
        for(int i = 0; i < 9; i++)
            for(int j = 0; j < 9; j++)
            {
                printf("%d", pic[i][j]);
                if(j == 8) printf("\n");
            }
    }
    return 0;
}

Sudoku

Time Limit: 2000MS		Memory Limit: 65536K
Total Submissions: 18750		Accepted: 9044		Special Judge

Description

Sudoku is a very simple task. A square table with 9 rows and 9 columns is divided to 9 smaller squares 3x3 as shown on the Figure. In some of the cells are written decimal digits from 1 to 9. The other cells are empty. The goal is to fill the empty cells with decimal digits from 1 to 9, one digit per cell, in such way that in each row, in each column and in each marked 3x3 subsquare, all the digits from 1 to 9 to appear. Write a program to solve a given Sudoku-task.

Input

The input data will start with the number of the test cases. For each test case, 9 lines follow, corresponding to the rows of the table. On each line a string of exactly 9 decimal digits is given, corresponding to the cells in this line. If a cell is empty it is represented by 0.

Output

For each test case your program should print the solution in the same format as the input data. The empty cells have to be filled according to the rules. If solutions is not unique, then the program may print any one of them.

Sample Input

Sample Output

Source

Southeastern Europe 2005