Catch that cow
Time limit:2000 ms |
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Memory limit:65536 K |
Total submissions:46279 |
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Accepted:14508 |
Description
Farmer John has been informed of the location of a fugitive cow and wants to catch her immediately. He starts at a pointN(0 ≤N≤ 100,000) on a number line and the cow is at a pointK(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 pointXTo the pointsX-1 orX+ 1 in a single minute
* Teleporting: FJ can move from any pointXTo the point 2 ×XIn 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:
NAnd
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. Idea: wide search for water problems.
1 /*====================================================================== 2 * Author : kevin 3 * Filename : CatchThatCow.cpp 4 * Creat time : 2014-08-03 10:06 5 * Description : 6 ========================================================================*/ 7 #include <iostream> 8 #include <algorithm> 9 #include <cstdio>10 #include <cstring>11 #include <queue>12 #include <cmath>13 #define clr(a,b) memset(a,b,sizeof(a))14 #define M 20000515 using namespace std;16 int vis[M],cnt[M];17 18 void BFS(int m,int n)19 {20 queue<int>que;21 vis[m]=1;22 que.push(m);23 while(que.front()!=n && !que.empty()){24 int t=que.front();25 que.pop();26 if(!vis[t-1] && (t-1>=0 && t-1<M)){27 que.push(t-1);28 cnt[t-1]=cnt[t]+1;29 vis[t-1]=1;30 }31 if(!vis[t+1] && (t+1>=0 && t+1<M)){32 que.push(t+1);33 cnt[t+1]=cnt[t]+1;34 vis[t+1]=1;35 }36 if(!vis[t*2] && (t*2>=0 && t*2<M)){37 que.push(t*2);38 cnt[t*2]=cnt[t]+1;39 vis[t*2]=1;40 }41 }42 }43 44 int main()45 {46 int n,k;47 while(scanf("%d%d",&n,&k)!=EOF){48 clr(vis,0);49 clr(cnt,0);50 BFS(n,k);51 printf("%d\n",cnt[k]);52 }53 return 0;54 }
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