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最新推荐文章于 2021-03-11 00:06:28 发布

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#宽度搜索

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本文介绍了一种解决旅行骑士问题中的子问题——寻找棋盘上两点间骑士行走的最短路径的算法实现。通过广度优先搜索(BFS)方法，程序能够计算出任意两点间所需的最少骑士跳跃次数。

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A friend of you is doing research on the Traveling Knight Problem (TKP) where you are to find the shortest closed tour of knight moves that visits each square of a given set of n squares on a chessboard exactly once. He thinks that the most difficult part of the problem is determining the smallest number of knight moves between two given squares and that, once you have accomplished this, finding the tour would be easy.
Of course you know that it is vice versa. So you offer him to write a program that solves the "difficult" part.

Your job is to write a program that takes two squares a and b as input and then determines the number of knight moves on a shortest route from a to b.

Input

The input file will contain one or more test cases. Each test case consists of one line containing two squares separated by one space. A square is a string consisting of a letter (a-h) representing the column and a digit (1-8) representing the row on the chessboard.

Output

For each test case, print one line saying "To get from xx to yy takes n knight moves.".

Sample Input

e2 e4
a1 b2
b2 c3
a1 h8
a1 h7
h8 a1
b1 c3
f6 f6

Sample Output

To get from e2 to e4 takes 2 knight moves.
To get from a1 to b2 takes 4 knight moves.
To get from b2 to c3 takes 2 knight moves.
To get from a1 to h8 takes 6 knight moves.
To get from a1 to h7 takes 5 knight moves.
To get from h8 to a1 takes 6 knight moves.
To get from b1 to c3 takes 1 knight moves.
To get from f6 to f6 takes 0 knight moves.

#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;
int flag[10][10];
int num[10][10];
char a[4],b[4];
int dir[10][2]={{-2,1},{-2,-1},{2,1},{2,-1},{-1,2},{-1,-2},{1,2},{1,-2}};
struct dian
{
   int x;
   int y;
}path[100];
void bfs(int x1,int y1,int x2,int y2)
{
  memset(flag,0,sizeof(flag));
  memset(num,0,sizeof(num));
  int head=0;
  int tail=1;
  path[head].x=x1;
  path[head].y=y1;
  num[x1][y1]=0;
  flag[x1][y1]=1;
  while(head<tail)
  {
   int x=path[head].x;
   int y=path[head].y;
   if(x==x2&&y==y2)
   {
    return ;
   }
   for(int i=0;i<8;i++)
   {
   int xx=x+dir[i][0];
   int yy=y+dir[i][1];
   if(flag[xx][yy]==0&&xx>=0&&xx<8&&yy>=1&&yy<9)
   {
    num[xx][yy]=num[x][y]+1;
    flag[xx][yy]=1;
    path[tail].x=xx;
    path[tail].y=yy;
    tail++;
   }
   }
   head++;
  }
}
int main()
{
    while(cin>>a>>b)
    {
     int x1=a[0]-'a';
     int y1=a[1]-'0';
     int x2=b[0]-'a';
     int y2=b[1]-'0';
     bfs(x1,y1,x2,y2);
     printf("To get from %s to %s takes %d knight moves.\n",a,b,num[x2][y2]);
    }
    return 0;
}