zoj 1091 Knight Moves

题目链接：http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=91

解题思路：BFS搜索

///////////////////////////////////////////////////////////////////////////
//problem_id: zoj 1091
//user_id: SCNU20102200088
///////////////////////////////////////////////////////////////////////////

#include <algorithm>
#include <iostream>
#include <iterator>
#include <iomanip>
#include <cstring>
#include <cstdlib>
#include <string>
#include <vector>
#include <cstdio>
#include <cctype>
#include <cmath>
#include <queue>
#include <stack>
#include <list>
#include <set>
#include <map>
using namespace std;

///////////////////////////////////////////////////////////////////////////
typedef long long LL;
const double PI=acos(-1.0);

const int x4[]={-1,0,1,0};
const int y4[]={0,1,0,-1};
const int x8[]={-1,-1,0,1,1,1,0,-1};
const int y8[]={0,1,1,1,0,-1,-1,-1};

typedef int T;
T max(T a,T b){ return a>b? a:b; }
T min(T a,T b){ return a<b? a:b; }
///////////////////////////////////////////////////////////////////////////

///////////////////////////////////////////////////////////////////////////
//Add Code:
int Ex,Ey,Min;
bool flag[10][10];
const int xx[]={-2,-1,1,2,2,1,-1,-2};
const int yy[]={1,2,2,1,-1,-2,-2,-1};

struct Node{
    int x,y,step;
    Node(int i,int j,int s):x(i),y(j),step(s){}
};

queue<Node> q;

void BFS(int i,int j){
    if(i==Ex && j==Ey){
        Min=0;
        return ;
    }
    memset(flag,0,sizeof(flag));
    flag[i][j]=1;
    Node node(i,j,0);
    q.push(node);
    while(!q.empty()){
        Node temp=q.front();
        q.pop();
        for(int p=0;p<8;p++){
            int x=temp.x+xx[p],y=temp.y+yy[p];
            if(x<1 || x>8 || y<1 || y>8 || flag[x][y]) continue;
            int step=temp.step+1;
            flag[x][y]=1;
            if(x==Ex && y==Ey){
                Min=step;
                while(!q.empty()) q.pop();
                return ;
            }
            else{
                Node res(x,y,step);
                q.push(res);
            }
        }
    }
}
///////////////////////////////////////////////////////////////////////////

int main(){
    ///////////////////////////////////////////////////////////////////////
    //Add code:
    char s[5],e[5];
    while(scanf("%s%s",s,e)!=EOF){
        int Sx=s[0]-'a'+1,Sy=s[1]-'0';
        Ex=e[0]-'a'+1,Ey=e[1]-'0';
        BFS(Sx,Sy);
        printf("To get from %s to %s takes %d knight moves.
",s,e,Min);
    }
    ///////////////////////////////////////////////////////////////////////
    return 0;
}

///////////////////////////////////////////////////////////////////////////
/*
Testcase:
Input:
e2 e4
a1 b2
b2 c3
a1 h8
a1 h7
h8 a1
b1 c3
f6 f6
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.
*/
///////////////////////////////////////////////////////////////////////////