POJ - 3278 Catch That Cow bfs 线性

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<queue>
using namespace std;
int a[],vis[];
queue<int>q;

int bfs(int n,int k)
{
    int head,next,i;
    q.push(n);
    a[n]=;
    vis[n]=;
    while(q.size()!=)
    {
        head=q.front();
        q.pop();
        for(i=;i<;i++)
        {
            if(i==)next=head-;
            else if(i==)next=head+;
            else if(i==)next=head*;
            if(next>=&&next<=)
            {
                if(vis[next]==)
                {
                    q.push(next);
                    a[next]=a[head]+;
                    vis[next]=;
                }
                if(next==k)
                    return a[next];
            }
        }
    }

}
int main()
{
    int i,j,n,k;
    while(scanf("%d%d",&n,&k)!=EOF)
    {
        memset(a,,sizeof(a));
        memset(vis,,sizeof(vis));
        while(!q.empty())q.pop();
        if(n>=k)
            printf("%d\n",n-k);
        else
        {
            printf("%d\n",bfs(n,k));
        }
    }
    return ;
}