poj 3278 Catch That Cow

直接 bfs，沒啥說了

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

int s,e,ans;
int queue[2000000];
bool visited[100002];

bool ok(int n){
	return n>=0&&n<=100000;
}

void bfs(){
	int front,rear;
	front=rear=0;
	queue[rear++]=s;
	queue[rear++]=0;
	while(front<rear){
		int first=queue[front++];
		int step=queue[front++];
		if(first==e){ans=step;return;}
		for(int i=0;i<3;i++){
			int tmp;
			if(i==0)tmp=first-1;
			if(i==1)tmp=first+1;
			if(i==2)tmp=first*2;
			if(ok(tmp)&&!visited[tmp]){
				if(tmp==e){ans=step+1;return;}
				visited[tmp]=true;
				queue[rear++]=tmp;
				queue[rear++]=step+1;
			}
		}
	}
}

int main(){

	while(scanf("%d%d",&s,&e)==2){
		memset(visited,false,sizeof(visited));
		visited[s]=true;
		ans=0;
		bfs();
		printf("%d\n",ans);

	}
}