poj2243

BFS

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#include <iostream>

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <queue>

using namespace std;



#define maxn 10



struct Point

{

    int x, y;

}s, t;



int dir[8][2] = {{1, 2}, {1, -2}, {-1, 2}, {-1, -2}, {2, 1}, {-2, 1}, {2, -1}, {-2, -1}};



bool in_bound(Point a)

{

    return a.x >= 0 && a.y >= 0 && a.x < 8 && a.y < 8;

}



int bfs()

{

    if (s.x == t.x && s.y == t.y)

        return 0;

    queue <Point> q;

    bool vis[maxn][maxn];

    int dist[maxn][maxn];

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

    q.push(s);

    vis[s.x][s.y] = true;

    dist[s.x][s.y] = 0;

    while (!q.empty())

    {

        Point a = q.front();

        q.pop();

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

        {

            Point b;

            b.x = a.x + dir[i][0];

            b.y = a.y + dir[i][1];

            if (in_bound(b) && !vis[b.x][b.y])

            {

                vis[b.x][b.y] = true;

                dist[b.x][b.y] = dist[a.x][a.y] + 1;

                q.push(b);

                if (b.x == t.x && b.y == t.y)

                    return dist[b.x][b.y];

            }

        }

    }

    return -1;

}



int main()

{

//    freopen("t.txt", "r", stdin);

    char st1[10], st2[10];

    while (~scanf("%s", st1))

    {

        s.x = st1[0] - 'a';

        s.y = st1[1] - '1';

        scanf("%s", st2);

        t.x = st2[0] - 'a';

        t.y = st2[1] - '1';

        printf("To get from %s to %s takes %d knight moves.\n", st1, st2, bfs());

    }

    return 0;

}