http://acm.hdu.edu.cn/showproblem.php?pid=1548
題意:一個電梯,在第 i 層只能選擇上或下k [ i ] 層(任何時候都不超過頂樓且不低於1樓),求從A到B層最少要按幾下電梯按鈕?
思路:BFS
#include<stdio.h>
#define maxn 222
typedef struct
{
int floor,go,cnt;//floor爲當先在的樓層,go爲可上、下樓層數,cnt爲當前步數
}node;
node quene[maxn], lift[maxn];
int n,a,b;
int bfs()
{
int front=0,rear=0,now=0,count=0;
quene[rear++]=lift[a];
while(front<rear)
{
now=quene[front].floor;
count=quene[front].cnt;
if(now+quene[front].go<=n&&!lift[now+quene[front].go].cnt)
{
lift[now+quene[front].go].cnt=count+1;
if(b==now+quene[front].go)
return 1;
quene[rear++]=lift[now+quene[front].go];
}
if(now-quene[front].go>0&&!lift[now-quene[front].go].cnt)
{
lift[now-quene[front].go].cnt=count+1;
if(b==now-quene[front].go)
return 1;
quene[rear++]=lift[now-quene[front].go];
}
front++;
}
return 0;
}
int main()
{
int i;
while(scanf("%d",&n)&&n)
{
scanf("%d %d",&a,&b);
for(i=1;i<=n;i++)
{
scanf("%d",&lift[i].go);
lift[i].cnt=0;
lift[i].floor=i;
}
if(a==b)
printf("0\n");
else if(bfs())
printf("%d\n",lift[b].cnt);
else
printf("-1\n");
}
return 0;
}