HDU 1548 A Strange Lift (search-deep search, wide search)

A Strange Lift Time limit:2000/1000 MS (java/others) Memory limit:65536/32768 K (java/others)
Total submission (s): 10384 Accepted Submission (s): 3888


Problem Description There is a strange lift. The lift can stop can at every floor as you want, and there are a number ki (0 <= ki <= N) on every floor. The lift has just, buttons:up, and down. When you are at floor i,if Press the button "up", you'll go up Ki floor,i.e,you'll go to the i+ki th floor,as the SAM E, if you press the button ' down ', you'll go down Ki floor,i.e,you'll go to the i-ki th floor. Of course, the lift can ' t go up high than n,and can ' t go down lower than 1. For example, there are a buliding with 5 floors, and K1 = 3, K2 = 3,K3 = 1,k4 = 2, K5 = 5.Begining from the 1st Floor,you Can press the button "up", and you'll go up to the 4th Floor,and if your press the button "down", the lift can ' t does it, be Cause it can ' t go down to the-2nd floor,as you know, the-2nd floor isn ' t exist.
Here comes the problem:when is on floor a,and you want to go to floor b,how many times at least he have to press the Button ' up ' or ' down '?

Input the input consists of several test Cases.,each test case contains the lines.
The first line contains three integers n, a, B (1 <= n,a,b <=) which describe above,the second line consist N int Egers k1,k2,.... kn.
A single 0 Indicate the end of the input.
Output for each case of the input output a interger, and the least times you had to press the button when you were on floor A,and You want to go to floor b.if your can ' t reach floor b,printf "-1".
Sample Input

5 1 5 3 3 1 2 5 0
Sample Output

3
Very simple deep search, pay attention to a small pruning on it.

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
# Include <queue>
#include <climits>

using namespace std;

const int MAX = 202;
int Flr[max],ans;
int Dist[max];
int n,b;

void Dfs (int s,int cnt) {
	if (s>n | | s<1) return;
	if (s==b) {
		if (Cnt<ans) {
			ans = cnt;
			return;
		}
	}
	if (Cnt>=dist[s]) return;
	Dist[s] = cnt;
	DFS (s+flr[s],cnt+1);
	DFS (s-flr[s],cnt+1);
}

int main () {
	//freopen ("In.txt", "R", stdin);

	int a,i,cnt;
	while (scanf ("%d", &n)!=eof && N) {
		scanf ("%d%d", &a,&b);
		for (i=1;i<=n;++i) {
			scanf ("%d", &flr[i]);
			Dist[i] = int_max-10;
		}
		CNT = 0;
		ans = Int_max;
		DFS (A,CNT);
		if (Ans==int_max) {
			printf (" -1\n");
		} else{
			printf ("%d\n", ans);
		}
	}

    return 0;
}

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