uva 439 - Knight Moves

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 Specification

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 Specification

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.

这个题就是开始还以为是一格一格走的，后面才知道原来是按中国象棋里面马的那种走法，那么做法就是从当前位置出发，不断扩张更新，在更新的过程中如果有相同位置情况就比较一下，最后输出：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int maze[10][10];//用于存储从起点到所在点的最小步数
int dir[8][2]={{-2,-1},{-2,1},{2,-1},{2,1},{1,2},{1,-2},{-1,2},{-1,-2}};//代表八个方向 
int x1,x2,y1,y2;//起点和终点坐标 
    
void dfs(int x,int y,int step){
    if(x==x2&&y==y2)return;
    for(int i=0;i<8;i++){
        int a=x+dir[i][0],b=y+dir[i][1];
        if((a>=0&&a<=7&&b>=0&&b<=7)&&(maze[a][b]==-1||maze[a][b]>step)){
            maze[a][b]=step;
            dfs(a,b,step+1);
        }
    }   
    return;
}    
 
int main(){
    char s1[5],s2[5];
    while(scanf("%s%s",s1,s2)!=EOF){
         memset(maze,-1,sizeof(maze)); 
         x1=s1[0]-97,x2=s2[0]-97,y1=s1[1]-49,y2=s2[1]-49;
         maze[x1][y1]=0;//起始点得注意 
         for(int i=0;i<8;i++){//遍历八个方向 
              int x=x1+dir[i][0], y=y1+dir[i][1];
              if(x>=0&&x<=7&&y>=0&&y<=7){//越的就不用再管了 
                  maze[x][y]=1;
                  dfs(x,y,2);
              } 
         }                
         printf("To get from %s to %s takes %d knight moves.\n",s1,s2,maze[x2][y2]);                
    } 
    return 0;
}