Catch That Cow
| Time Limit: 2000MS | Memory Limit: 65536K | |
| Total Submissions: 112355 | Accepted: 35099 |
Description
Farmer John has been informed of the location of a fugitive cow and wants to catch her immediately. He starts at a point N (0 ≤ N ≤ 100,000) on a number line and the cow is at a point K (0 ≤ K ≤ 100,000) on the same number line. Farmer John has two modes of transportation: walking and teleporting.
* Walking: FJ can move from any point X to the points X - 1 or X + 1 in a single minute
* Teleporting: FJ can move from any point X to the point 2 × X in a single minute.
If the cow, unaware of its pursuit, does not move at all, how long does it take for Farmer John to retrieve it?
Input
Line 1: Two space-separated integers:
N and
K
Output
Line 1: The least amount of time, in minutes, it takes for Farmer John to catch the fugitive cow.
Sample Input
5 17
Sample Output
4
Hint
The fastest way for Farmer John to reach the fugitive cow is to move along the following path: 5-10-9-18-17, which takes 4 minutes.
比较坑的是队列不能定义在函数内部，要定义为全局变量，不然会WA。可能这题对队列容量需求确实比较大，定义为全局变量可以获得更大的队列空间。不过要记得每次清空。
#include <cstdio>
#include <iostream>
#include <algorithm>
#include <string>
#include <cstring>
#include <cmath>
#include <queue>
#include <stack>
#include <sstream>
#include <map>
#define INF 10000
using namespace std;
int n,k;
int vis[200005];
struct DATA
{
int v,step;
DATA(int vv,int ss)
{
v=vv;
step=ss;
}
};
typedef struct DATA DATA;
queue<DATA> Q;
int BFS()
{
DATA s(n,0);
Q.push(s);
vis[n]=1;
while(Q.size()>0)
{
DATA cur=Q.front();
Q.pop();
if(cur.v==k)
{
return cur.step;
}
int cv=cur.v;
int cs=cur.step;
if(cv>0 && vis[cv-1]==0)
{
DATA tmp(cv-1,cs+1);
vis[cv-1]=1;
Q.push(tmp);
}
if(cv<=k && vis[cv+1]==0)
{
DATA tmp(cv+1,cs+1);
vis[cv+1]=1;
Q.push(tmp);
}
if(cv<=k && vis[cv*2]==0)
{
DATA tmp(cv*2,cs+1);
vis[cv*2]=1;
Q.push(tmp);
}
}
}
int main()
{
while(scanf("%d%d",&n,&k)==2)
{
memset(vis,0,sizeof(vis));
if(n>=k)
{
printf("%d\n",n-k);
continue;
}
while(Q.size()>0) Q.pop();
int ans=BFS();
printf("%d\n",ans);
}
return 0;
}