POJ 2918 求解数独

思路：dfs，试填每个方格，当搜索的范围超过9×9时说明已经找到解

#include<cstdio>#include<string>#include<cstring>#include<iostream>#include<algorithm>using namespace std; int map[15][15], flag; bool CanPlace(int x, int y, int num){    for(int i = 1; i <= 10; i ++)         if(map[x][i] == num || map[i][y] == num) return false;     int row = ((x-1)/3)*3+1;     int col = ((y-1)/3)*3+1;     for(int i = row; i < row+3; i ++){        for(int j = col;j < col+3; j ++ )            if(map[i][j] == num) return false;     }    return true; }void dfs(int x, int y){    if(x == 9 && y > 9){        flag = 1;         for(int i = 1; i < 10; i ++){            for(int j = 1; j < 10; j ++) printf("%d", map[i][j]);             printf("\n");         }        return;     }    if(y > 9){        x++;         y = 1;     }    if(!map[x][y]){        for(int i = 1;i < 10; i ++){            if(CanPlace(x, y, i)){                map[x][y] = i;                 dfs(x, y+1);                 if(flag) return;                 map[x][y] = 0;             }        }    }else dfs(x, y+1); }int main(){    char str[11];     int t,cnt = 0;     //freopen("in.c", "r", stdin);     scanf("%d", &t);     while(t--){        printf("Scenario #%d:\n", ++cnt);         memset(str, 0, sizeof(str));         for(int i = 0; i < 9; i ++){            scanf("%s", str);             for(int j = 0; j < 9; j ++){                map[i+1][j+1] = str[j]-'0';             }        }        flag = 0;         dfs(1, 1);         puts("");     }    return 0; }