首页 > 代码库 > POJ 3278 Catch That Cow（bfs）
POJ 3278 Catch That Cow（bfs）
传送门
Catch That Cow
| Time Limit: 2000MS | Memory Limit: 65536K | |
| Total Submissions: 80273 | Accepted: 25290 |
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 17Sample Output
4Hint
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.
思路
题意：给定起点和终点，有三种走的方式，假设当前为 now，那么可以选择下一次到达 now - 1 或 now + 1 或 2*now，问起点到终点最少需要几步。
题解：bfs，下一个状态即为三种可选择的位置。
#include<iostream>#include<cstdio>#include<cstring>using namespace std;const int maxn = 100005;int step[maxn],que[maxn],vis[maxn];int bfs(int st,int ed){ int E = 0,F = 0; que[F++] = st; vis[st] = 1; for (;;) { int now = que[E]; if (now == ed) return step[now]; if (now + 1 < maxn && !vis[now + 1]) step[now + 1] = step[now] + 1,vis[now + 1] = 1,que[F++] = now + 1; if (now - 1 >= 0 &&!vis[now - 1]) step[now - 1] = step[now] + 1,vis[now - 1] = 1,que[F++] = now - 1; if (2*now < maxn && !vis[2*now]) step[2*now] = step[now] + 1,vis[2*now] = 1,que[F++] = 2 * now; E++; }}int main(){ int N,K; memset(vis,0,sizeof(vis)); scanf("%d%d",&N,&K); if (N >= K) printf("%d\n", N - K); else printf("%d\n",bfs(N,K)); return 0;}
POJ 3278 Catch That Cow（bfs）
声明：以上内容来自用户投稿及互联网公开渠道收集整理发布，本网站不拥有所有权，未作人工编辑处理，也不承担相关法律责任，若内容有误或涉及侵权可进行投诉： 投诉/举报 工作人员会在5个工作日内联系你，一经查实，本站将立刻删除涉嫌侵权内容。