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POJ2488A Knight's Journey[DFS]

A Knight‘s Journey
Time Limit: 1000MS Memory Limit: 65536K
Total Submissions: 41936 Accepted: 14269

Description

技术分享Background 
The knight is getting bored of seeing the same black and white squares again and again and has decided to make a journey 
around the world. Whenever a knight moves, it is two squares in one direction and one square perpendicular to this. The world of a knight is the chessboard he is living on. Our knight lives on a chessboard that has a smaller area than a regular 8 * 8 board, but it is still rectangular. Can you help this adventurous knight to make travel plans? 

Problem 
Find a path such that the knight visits every square once. The knight can start and end on any square of the board.

Input

The input begins with a positive integer n in the first line. The following lines contain n test cases. Each test case consists of a single line with two positive integers p and q, such that 1 <= p * q <= 26. This represents a p * q chessboard, where p describes how many different square numbers 1, . . . , p exist, q describes how many different square letters exist. These are the first q letters of the Latin alphabet: A, . . .

Output

The output for every scenario begins with a line containing "Scenario #i:", where i is the number of the scenario starting at 1. Then print a single line containing the lexicographically first path that visits all squares of the chessboard with knight moves followed by an empty line. The path should be given on a single line by concatenating the names of the visited squares. Each square name consists of a capital letter followed by a number. 
If no such path exist, you should output impossible on a single line.

Sample Input

31 12 34 3

Sample Output

Scenario #1:A1Scenario #2:impossibleScenario #3:A1B3C1A2B4C2A3B1C3A4B2C4

Source

TUD Programming Contest 2005, Darmstadt, Germany


该死行走数组写错了该死该死该死
////  main.cpp//  poj2488////  Created by Candy on 9/27/16.//  Copyright © 2016 Candy. All rights reserved.//#include <iostream>#include <cstdio>#include <algorithm>#include <cstring>using namespace std;const int N=50;inline int read(){    char c=getchar();int x=0,f=1;    while(c<0||c>9){if(c==-)f=-1;c=getchar();}    while(c>=0&&c<=9){x=x*10+c-0;c=getchar();}    return x;}int T,n,m,sum,vis[N][N],flag=0,cas=0;struct data{    int x,y;    data(int a=0,int b=0):x(a),y(b){}}path[N];int dx[8]={-1,1,-2,2,-2,2,-1,1},dy[8]={-2,-2,-1,-1,1,1,2,2};void print(){    for(int i=1;i<=sum;i++){        int x=path[i].x,y=path[i].y;        printf("%c%d",A-1+y,x);    }}void dfs(int x,int y,int d){//printf("dfs %d %d %d\n",x,y,d);    path[d]=data(x,y);    if(d==sum){flag=1;return;}    for(int i=0;i<8;i++){        int nx=x+dx[i],ny=y+dy[i];        if(nx>=1&&nx<=n&&ny>=1&&ny<=m&&!vis[nx][ny]&&!flag){            vis[nx][ny]=1;            dfs(nx,ny,d+1);            vis[nx][ny]=0;        }    }}int main(int argc, const char * argv[]) {    T=read();    while(T--){        n=read();m=read();        sum=n*m; flag=0;        memset(vis,0,sizeof(vis));        vis[1][1]=1;        dfs(1,1,1);        printf("Scenario #%d:\n",++cas);        if(!flag) printf("impossible");else print();        printf("\n\n");    }    return 0;}

 

POJ2488A Knight's Journey[DFS]