标签：
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
Output
Sample Input
5 17
Sample Output
4
Hint
#include"cstdio" #include"queue" #include"cstring" using namespace std; typedef pair<int,int> P; const int MAXN=100005; int vis[MAXN]; int n,k; int bfs() { queue<P> que; vis[n]=1; que.push(P(0,n)); while(!que.empty()) { P now = que.front();que.pop(); if(now.second==k) { return now.first; } for(int i=-1;i<=1;i++) { int next; if(i==0) next=now.second*2; else next=now.second+i; if(next>=0&&next<=MAXN&&!vis[next])//注意条件不能少，且顺序不能颠倒 { vis[next]=1; que.push(P(now.first+1,next)); } } } return -1; } int main() { while(scanf("%d%d",&n,&k)!=EOF) { memset(vis,0,sizeof(vis)); printf("%d\n",bfs()); } return 0; }
标签：
原文地址：http://www.cnblogs.com/program-ccc/p/5001925.html
