Catch That Cow

5 17

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.
 

USACO 2007 Open Silver 

bfs注意注释的几个地方，坑哭我了，，，只怪自己太菜

#include<stdio.h>
#include<string.h>
#include<queue>
using namespace std;
int vis[110000];
int n,k;
struct node{
	int val,d;
}s,num;

int bfs(){
	memset(vis,0,sizeof(vis));
	queue <node> Q;
	while(!Q.empty()) Q.pop();
	s.val=n; s.d=0;
	vis[n]=1;
	Q.push(s);
	while(!Q.empty()){
		s=Q.front();
		Q.pop();
		for(int i=0;i<3;i++){
			if(i==0) num.val=s.val+1;
			if(i==1) num.val=s.val-1;
			if(i==2) num.val=s.val*2;
			num.d=s.d+1;
			if(num.val==k) return num.d;
			if(num.val<0 || num.val>110000)//原来写的num.val>k，wa了20多次，草，fuck，，， 
				continue;
			//if(num.val>=0&&!vis[num.val]&&num.val<100000){//这样写num.val大于110000是，vis数组就会溢出 
			if(!vis[num.val]){ 
				vis[num.val]=1;
				Q.push(num);
			}
 		}
	}
	return -1;	
}
int main(){
	while(scanf("%d%d",&n,&k)!=EOF){
		if(n>k) printf("%d\n",n-k);
		else if(n==k) printf("0\n");
		else 
			printf("%d\n",bfs());
	}
	return 0;
}

hdu 2717 && poj 3278 Catch That Cow

原文：http://blog.csdn.net/ling_du/article/details/47314035