学步园

BFS的一道水题，上学之前AC掉:-) 直接BFS即可

/*
 * HDU-???? catch that cow
 * mike-w
 * 2012-9-25
 */
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#define QSIZE 222222

int que[QSIZE], qhead, qtail, qlen;
int rec[QSIZE];

int enque(int e)
{
	qlen++;
	que[qtail++]=e;
	qtail%=QSIZE;
	return 0;
}

int deque(void)
{
	int ret=que[qhead++];
	qhead%=QSIZE;
	qlen--;
	return ret;
}

int main(void)
{
	int n, k, x;
	while(scanf("%d%d", &n, &k)!=EOF)
	{
		qhead=qtail=qlen=0;
		memset(rec, 0, sizeof(rec));
		memset(que, 0, sizeof(que));
		enque(n);
		while(qlen>0)
		{
			x=deque();
			if(x==k)
				break;
			if(x+1<=2*k && !rec[x+1])
				rec[x+1]=rec[x]+1, enque(x+1);
			if(x-1>=0 && !rec[x-1])
				rec[x-1]=rec[x]+1, enque(x-1);
			if(x<=k && !rec[2*x])
				rec[2*x]=rec[x]+1, enque(2*x);
		}
		printf("%d\n", rec[x]);
	}
	return 0;
}