UVa-439 Knight Moves

#include <bits/stdc++.h>
using namespace std;
struct Node
{
    int r,c;
    Node(int a,int b) : r(a),c(b) {}
    Node() {}
};
const int dr[] = {-2,-2,-1,-1,1,1,2,2};
const int dc[] = {-1,1,-2,2,-2,2,-1,1};

int r1,c1,r2,c2;
string in1,in2;
void read()
{
    r1 = 8-(in1[1]-'0');c1 = in1[0]-'a';
    cin >> in2;r2 = 8-(in2[1]-'0');c2 = in2[0]-'a';
}

int d[9][9];
bool limit(Node u)
{
    return u.r>=0&&u.r<=7&&u.c>=0&&u.c<=7;
}
int solve()
{
    memset(d,-1,sizeof(d));
    queue<Node> q;
    q.push(Node(r1,c1));
    d[r1][c1] = 0;
    while(!q.empty())
    {
        Node u = q.front();
        q.pop();
        if(u.r==r2&&u.c==c2)    return d[r2][c2];
        for(int i = 0; i < 8; i ++)
        {
            Node v = u;
            v.r += dr[i];
            v.c += dc[i];
            if(limit(v)&&d[v.r][v.c]<0)
            {
                d[v.r][v.c] = d[u.r][u.c] + 1;
                q.push(v);
            }
        }
    }
}

void print(int rnt)
{
    cout << "To get from " <<in1<< " to " <<in2<< " takes " <<rnt<< " knight moves." << endl;
}
int main()
{
    while(cin >> in1)
    {
        read();
        int rnt = solve();
        print(rnt);
    }
    return 0;
}