# 【BZOJ1646】[Usaco2007 Open]Catch That Cow 抓住那只牛

## 描述 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?

## 输入格式 InputFormat

Line 1: Two space-separated integers: N and K.

## 输出格式 OutputFormat

Line 1: The least amount of time, in minutes, it takes for Farmer John to catch the fugitive cow.

123 999

6

Silver

BZOJ 1646

## 代码 Code

BFS.

``````#include <stdio.h>
#include <iostream>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
#define inf 0x7fffffff/27.11
const int maxN=200000;
int a[200005];
int f[1000005];
int i,j,t,n,m,l,r,k,z,y,x;
{
f[++r]=s;
a[s]=a[f[l]]+1;
}
void bfs()
{
int i,j,t;
l=0;r=0;f[0]=n;a[n]=0;
while (r>=l)
{
if (f[l]==k) return ;