hdoj 2717 Catch That Cow

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2717

基本BFS求最短路径。

//2013-12-03 10:44:00    Accepted    2717    15MS    840K    1143 B    C++    空信高手

#include <iostream>

#include <queue>

using namespace std;







#define MAX 100001

int d[MAX];

int N,K;

void BFS()

{

    memset(d,0,sizeof(d));

    queue<int> q;

    q.push(N);



    while(!q.empty())

    {

        int u=q.front();

        if(u==K) return;

        q.pop();



        int next=u-1;

        if(next>=0&&next<MAX&&!d[next])

        {

            q.push(next);

            d[next]=d[u]+1;

        }

        next=u+1;

        if(next>=0&&next<MAX&&!d[next])

        {

            q.push(next);

            d[next]=d[u]+1;

        }

        next=2*u;

        if(next>=0&&next<MAX&&!d[next])

        {

            q.push(next);

            d[next]=d[u]+1;

        }

    }

}

int main()

{

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

    while(scanf("%d%d",&N,&K)!=EOF)

    {

        if(N==K)

            printf("0\n");

        else

        {

            BFS();

            printf("%d\n",d[K]);

        }

    }

    return 0;

}