bzoj 1646: [Usaco2007 Open]Catch That Cow 抓住那只牛【bfs】

满脑子dp简直魔性
模拟题意bfs转移即可

#include<iostream>
#include<cstdio>
#include<queue>
using namespace std;
const int N=200005;
int s,t,d[N];
bool v[N];
queue<int>q;
inline void wk(int x,int y)
{
	d[y]=d[x]+1;
	if(!v[y])
	{
		v[y]=1;
		q.push(y);
	}
}
int main()
{
	scanf("%d%d",&s,&t);
	for(int i=0;i<=200000;i++)
		d[i]=1e9;
	v[s]=1,d[s]=0,q.push(s);
	while(!q.empty())
	{
		int u=q.front();
		q.pop();
		v[u]=0;
		if(u*2<=200000&&d[u*2]>d[u]+1)
			wk(u,u*2);
		if(u+1<=200000&&d[u+1]>d[u]+1)
			wk(u,u+1);
		if(u-1>=0&&d[u-1]>d[u]+1)
			wk(u,u-1);
	}
	printf("%d\n",d[t]);
	return 0;
}