spoj knight moves

#include<bits/stdc++.h>
using namespace std;

struct Node
{
	int x,y;

};

int row[] = { 2, 2, -2, -2, 1, 1, -1, -1 };
int col[] = { -1, 1, 1, -1, 2, -2, 2, -2 };

bool vis[100][100];
int dis[100][100]={0};


bool isValid(int x, int y, int N) {
    return (x >= 0 && x < N) && (y >= 0 && y < N);
}



int bfs(Node src, Node dest, int N)
{


    queue<Node> q;

    q.push(src);
    vis[src.x][src.y]=1;
    dis[src.x][src.y]=0;

    while(!q.empty())
    {
        Node node = q.front();
        q.pop();

        int x = node.x;
        int y = node.y;


        // if the destination is reached, return distance
        if (x == dest.x && y == dest.y) {
            return dis[x][y];
        }

        for (int i = 0; i < 8; i++)
        {

            int x1 = x + row[i];
            int y1 = y + col[i];

            if (isValid(x1, y1, N) && !vis[x1][y1])
            {
                q.push({x1, y1});
                vis[x1][y1]=1;
                dis[x1][y1]= dis[node.x][node.y]+1;
            }

        }
    }
    return 1;

}



int main(int argc, char** argv)
{


#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif


    // N x N matrix
    int N = 8;
    int p;

    std::map<char, int> m;

    for (struct { int a; char b; } s = { 0, 'a' } ; s.a < 8; ++s.a, s.b++)
    {
    	m[s.b]=s.a;

    }


    cin>>p;

    for (int i = 0; i < p; ++i)
    {
    	string s1,s2;
    	cin>>s1>>s2;

    	int srcX = m[s1[0]];
    	int srcY = (s1[1]-'0')-1;


    	int desX = m[s2[0]];
    	int desY = (s2[1]-'0')-1;

    	//cout<<srcX<<srcY<<" "<<desX<<desY<<endl;

    Node src = {srcX, srcY};

    // destination coordinates
    Node dest = {desX, desY};

    cout <<bfs(src, dest, N)<<endl;

     memset(dis, 0, sizeof(dis));
     memset(vis, 0, sizeof(vis));



    }



}