SDAU课程练习2 1015

Knight Moves

Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 65536/32768K (Java/Other)

Total Submission(s) : 14   Accepted Submission(s) : 6

Problem Description

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.<br>Of course you know that it is vice versa. So you offer him to write a program that solves the &quot;difficult&quot; part. <br><br>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. <br>

 

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. <br>

 

Output

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

 

Sample Input

e2 e4<br>a1 b2<br>b2 c3<br>a1 h8<br>a1 h7<br>h8 a1<br>b1 c3<br>f6 f6<br>

 

Sample Output

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

 

Source

University of Ulm Local Contest 1996

 

题目大意：

和中国象棋一样的走法，给出起点和终点坐标，求出最少步数。

思路：

上课讲过的例题，bfs 八个方向就行了。

感想：

我没啥好说的，自动略过~~

AC代码：

#include<iostream>#include<string.h>#include<queue>#include<stdio.h>using namespace std;int vis[20][20];string s1,s2;struct ans{    int x;    int y;    int ste;}n1,n2;int dix[10]={-2,-2,-1,-1,1,1,2,2};int diy[10]={-1,1,-2,2,-2,2,-1,1};int ww(int a,int b){    if(a>0&&a<=8&&b>0&&b<=8) return 1;    return 0;}int BFS( ){    n1.ste=0;    queue<ans> Q;    Q.push(n1);    while(!Q.empty())    {        n1=Q.front();        Q.pop();        if(n1.x==s2[1]-'0'&&n1.y==s2[0]-'a'+1) return n1.ste;        for(int i=0;i<8;i++)        {            n2.x=n1.x+dix[i];            n2.y=n1.y+diy[i];            if(ww(n2.x,n2.y)&&!vis[n2.x][n2.y])            {                vis[n2.x][n2.y]=1;                n2.ste=n1.ste+1;                Q.push(n2);            }        }    }    return -1;}int main(){    //freopen("a.txt","r",stdin);    while(cin>>s1>>s2)    {        int i,j;        n1.x=s1[1]-'0';        n1.y=s1[0]-'a'+1;        for(i=0;i<20;i++)            for(j=0;j<20;j++)             vis[i][j]=0;        vis[n1.x][n1.y]=1;        int t=BFS();            cout<<"To get from "<<s1<<" to "<<s2<<" takes "<<t<<" knight moves."<<endl;    }    return 0;}