A Knight's Journey(P2488)

一道比较简单的搜索题，自己也是一次过，过得比较爽。哈哈。。

#include<iostream>
#include<stdlib.h>
#include<math.h>
#include<stdio.h>
#include<algorithm>
#include<queue>
#include<string.h>
#include<stack>
#include<math.h>
#include<stdlib.h>
#include<list>
#include<vector>

using namespace std;


int fang[8][2]={{-2,-1},{-2,1},{-1,-2},{-1,2},{1,-2},{1,2},{2,-1},{2,1}};
int lie,heng;
bool a[100][100];
char go[100]="aABCDEFGHIJKLMNOPQRSTUVWXYZ";
int ans;
int xx[100],yy[199];
int lx,ly;


bool in (int i,int j)
{
    if (i<1||i>lie)
        return false;
    if (j<1||j>heng)
        return false;
    return true;
}

bool dfs(int i,int j)
{
//    cout<<i<<' '<<j<<endl;
    int k;
    if (ans==lie*heng)
    {
        return false;
    }
    bool f=true;;
    for (k=0;k<8;k++)
    {
        int x=fang[k][0]+i;
        int y=fang[k][1]+j;
        if (in(x,y)&&!a[x][y])
        {
            a[x][y]=true;
            xx[ans]=x;
            yy[ans]=y;
            ans++;
            f= dfs(x,y);
            if (!f)
            {
                break;
            }
            ans--;
            a[x][y]=false;
        }
    }
    return f;
}

int main()
{
    int i,j,k;
    int t;
    cin>>t;
    int num=0;
    while (t--)
    {
        lx=0;
        ly=0;
        num++;
        ans=1;
        cin>>heng>>lie;
        memset(a,false,sizeof(a));
        a[1][1]=true;
        
        cout<<"Scenario #"<<num<<':'<<endl;
        if (dfs(1,1) )
        {
            //cout<<ans<<endl;
            cout<<"impossible"<<endl<<endl;
            continue;
        }
        xx[0]=1;
        yy[0]=1;
        for (i=0;i<lie*heng;i++)
            cout<<go[xx[i]]<<yy[i];
        cout<<endl<<endl;
            
    }

}

A Knight's Journey

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 18979		Accepted: 6377

Description

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 1 2 3 4 3

Sample Output

Scenario #1:A1 Scenario #2: impossible Scenario #3: A1B3C1A2B4C2A3B1C3A4B2C4

Source

TUD Programming Contest 2005, Darmstadt, Germany