POJ3278 Catch That Cow 简单BFS

题解：

简单的BFS，就不说什么了，唯一注意的是要判断是不是越界了

代码

#include <cstdio>
#include <queue>
#include <cstring>
#include <iostream>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <map>
#include <string>
#include <set>
#include <ctime>
#include <cmath>
#include <cctype>
using namespace std;
#define MAX 100000
#define LL long long
int cas=1,T;
struct Node
{
int temp;
int step;
};
queue<Node> que;
int vis[100000+10];
bool check(int n)
{
if (n<0 || n>100000 )
return true;
else if (vis
)
return true;
return false;
}
int main()
{
int n,k;
scanf("%d%d",&n,&k);
if (n>=k)
printf("%d\n",n-k);
else
{
Node q;
q.temp=n;
q.step=0;
que.push(q);
int flag = 0;
while (!que.empty())
{
Node t = que.front();
que.pop();
if (t.temp==k)
{
flag = 1;
printf("%d\n",t.step);
break;
}

for (int i = 0;i<3;i++)
{
Node a= t;
if (i==0)
{
a.temp--;
if (check(a.temp))
continue;
a.step++;
que.push(a);
vis[a.temp]=1;
}
if (i==1)
{
a.temp++;
if (check(a.temp))
continue;
a.step++;
que.push(a);
vis[a.temp]=1;
}
if (i==2)
{
a.temp = a.temp *2;
if (check(a.temp))
continue;
a.step++;
que.push(a);
vis[a.temp]=1;
}
}
}
if (!flag)
printf("-1\n");
memset(vis,0,sizeof(vis));

}
//freopen("in","r",stdin);
//scanf("%d",&T);
//printf("time=%.3lf",(double)clock()/CLOCKS_PER_SEC);
return 0;
}

题目

Time Limit:2000MS Memory Limit:65536KB 64bit IO Format:%I64d & %I64u

Submit

Status

Practice

POJ 3278

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