UVa 439 - Knight Move

#include<iostream>
#include<algorithm>
#include<queue>
#include<map>
#include<vector>
#include<cstdio>
#include<cstdlib>
#include<cstring>

using namespace std;

#define ll long long

#define PII pair<int,int>

int dx[] = { -2, -1, -2, -1, 1, 2, 2, 1 };
int dy[] = { -1, -2, 1, 2, 2, 1, -1, -2 };

ll level[8][8] = {};

ll BFS(PII src, PII dst)
{
    queue< PII > q ;
    q.push(src) ;
    level[src.first][src.second] = 1 ;

    while(!q.empty())
    {
        PII now ;
        now = q.front();
        q.pop();

        for(ll i = 0 ; i< 8 ; i++)
        {
            ll tx, ty ;
            tx = now.first + dx[i] ;
            ty = now.second + dy[i] ;

            if(tx >= 0 && tx< 8 && ty >=0 && ty< 8 )
            {
                if(level[tx][ty]==0)
                {
                    level[tx][ty] = level[now.first][now.second] + 1 ;
                    q.push(make_pair(tx, ty)) ;
                }
                else
                {
                    if(level[tx][ty] > level[now.first][now.second] + 1)
                    {
                        level[tx][ty] = level[now.first][now.second] + 1 ;
                    }
                }
            }
        }
    }

    return level[dst.first][dst.second] ;

}

int main()
{
//    freopen("in.txt","r",stdin);
    char s1[5], s2[5] ;
    ll ans;
    while(scanf(" %s %s", s1, s2)!= EOF)
    {
        ll r1, r2, c1, c2 ;
        r1 = s1[1] - '0' - 1 ;
        r2 = s2[1] - '0' -1 ;
        c1 = s1[0] - 'a'  ;
        c2 = s2[0] - 'a'  ;

        PII src, dst ;
        src = make_pair(r1, c1) ;
        dst = make_pair(r2, c2) ;

        ans = BFS(src,dst) - 1;

        printf("To get from %s to %s takes %lld knight moves.\n", s1, s2, ans ) ;

        memset(level, 0, sizeof(level));
    }


}