pku acm 3278源码

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

int n,k;
const int N=100001;
int Q[N];
int visited[N];
int ans[N];

int bfs(int x)
{
if (x>=k)
return (x-k);

visited[x]=1;
Q[0]=x;
int first=-1,last=0;

while (first!=last)
{
int v=Q[++first];

if (v==k)
return ans[v];

int tmpx=v+1;
if (tmpx>=0 && tmpx<N &&visited[tmpx]==0)
{
Q[++last]=tmpx;
visited[tmpx] = 1;
ans[tmpx]=ans[v]+1;
}

tmpx=v-1;
if (tmpx>=0 && tmpx<N &&visited[tmpx]==0)
{
Q[++last]=tmpx;
visited[tmpx] = 1;
ans[tmpx]=ans[v]+1;
}

tmpx=v*2;
if (tmpx>=0 && tmpx<N &&visited[tmpx]==0)
{
Q[++last]=tmpx;
visited[tmpx] = 1;
ans[tmpx]=ans[v]+1;
}
}
}

int main()
{
while(cin>>n>>k)
{
memset(visited,0,sizeof(visited));
memset(Q,0,sizeof(Q));
memset(ans,0,sizeof(ans));
cout<<bfs(n)<<endl;
}
return 0;
}