dfs + 回溯

hdoj 1426 Sudoku Killer

数独

#include <iostream>
using namespace std;
 
struct Node {
    int x, y;
}ns[85];
 
int cntSum, ca=1;
int mp[10][10];
 
bool init() {
    int i, j;
    char ch[5];
    cntSum = 0;
    for( i=0; i<9; ++i ) {
        for( j=0; j<9; ++j ) {
            if( scanf( "%s", ch ) == EOF ) return 0;
            if( ch[0] == '?' ) {
                ns[cntSum].x = i;
                ns[cntSum++].y = j;
                mp[i][j] = 0;
            } else {
                mp[i][j] = ch[0] - '0';
            }
        }
    }
}
 
 
bool canPut( int deep, int v ) {
    int x, y, i, j, a, b;
    x = ns[deep].x;
    y = ns[deep].y;
    for( i=0; i<9; ++i ) if( i != y && mp[x][i] == v ) return 0;
    for( i=0; i<9; ++i ) if( i != x && mp[i][y] == v ) return 0;
    a = x / 3;
    b = y / 3;
    for( i=a*3; i<=a*3+2; ++i ) {
        for( j=b*3; j<=b*3+2; ++j ) {
            if( i!=x && j!=y && mp[i][j] == v ) return 0;
        }
    }
    return 1;
}
     
 
bool dfs( int deep) {
    if( deep >= cntSum ) return 1;
    for( int i=1; i<=9; ++i ) {
        if( canPut( deep, i ) ) {
            mp[ns[deep].x][ns[deep].y] = i;
            if( dfs( deep+1) ) return 1;
            mp[ns[deep].x][ns[deep].y] = 0;
        }
    }
    return 0;
}  
 
 
void solve() {
    int i;
    for( i=1; i<=9; ++i ) {
        if( canPut(0, i) ) {
            mp[ns[0].x][ns[0].y] = i;
            if( dfs( 1 ) ) return;
            mp[ns[0].x][ns[0].y] = 0;
        }
    }
}
 
 
void Print() {
    int i, j;
    if( ca != 1 ) printf( "\n" );
    ++ ca;
    for( i=0; i<9; ++i ) {
        for( j=0; j<9; ++j ) {
            if( j!= 0 ) putchar( ' ' );
            printf( "%d", mp[i][j] );
        }
        printf( "\n" );
    }
}
 
 
int main() {
//  freopen( "c:/aaa.txt", "r", stdin );
    int i, j;
    char ch[5];
    while( init() ) {
        solve();
        Print();
    }
    return 0;
}