poj 3278 bfs

题目大意：FJ要去抓牛...

思路：bfs即可

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;

const int N = 100001;
bool visit[N];

struct Node
{
    int x, step;

    Node () {}

    Node ( int _x, int _step )
    {
        x = _x, step = _step;
    }

} q[N];

bool ok( int x )
{
    return x >= 0 && x < N && !visit[x];
}

int bfs( int src, int des )
{
    memset( visit, 0, sizeof(visit) );
    int head = 0, tail = 0;
    q[tail++] = Node( src, 0 );
    visit[src] = 1;
    while ( head < tail )
    {
        Node t = q[head++];
        if ( t.x == des ) return t.step;
        if ( ok( t.x + 1 ) )
        {
            q[tail++] = Node( t.x + 1, t.step + 1 );
            visit[t.x + 1] = 1;
        }
        if ( ok( t.x - 1 ) )
        {
            q[tail++] = Node( t.x - 1, t.step + 1 );
            visit[t.x - 1] = 1;
        }
        if ( ok( t.x * 2 ) )
        {
            q[tail++] = Node( t.x * 2, t.step + 1 );
            visit[t.x * 2] = 1;
        }
    }
    return -1;
}

int main()
{
    int s, t;
    while ( scanf("%d%d", &s, &t) != EOF )
    {
        printf("%d
", bfs( s, t ));
    }
    return 0;
}