POJ 3278

#include<iostream>
#include<cstring>
#include<math.h>
#include<queue>
using namespace std;
const int MAX=1000000;
int n,k;
queue<int> q;
int vis[MAX];
int op[3]={1,-1,2};
int t[MAX];
int bfs(){
	q.push(n);
	vis[n]=1;
	while(!q.empty()){
		int t1,t2;
		t1=q.front();
		q.pop();
		if(t1==k)
			return t[t1]; 
		for(int i=0;i<3;i++){
			if(i==2){
				t2=t1*2;
			}else{
				t2=t1+op[i];
			}
			if(t2>=0&&t2<MAX){
				if(!vis[t2]){
				vis[t2]=1;
				t[t2]=t[t1]+1; 
				q.push(t2);	
				}
			}else
				continue; 
		}
	}
}
int main(){
	memset(vis,0,sizeof(vis));
	memset(t,0,sizeof(t));
	while(!q.empty()) q.pop();
	cin>>n>>k; 
	if(n>=k)
		cout<<n-k;
	else
		cout<<bfs(); 
	return 0;
}

http://poj.org/problem?id=3278

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.