记录编号	154696	评测结果	AAAAAAAAAA
题目名称	[HDU 1548] 奇怪的电梯	最终得分	100
用户昵称	devil	是否通过	通过
代码语言	C++	运行时间	0.008 s
提交时间	2015-03-23 22:54:05	内存使用	0.31 MiB

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <map>
#include <queue>
#include <cstring>
#include <sstream>
#include <algorithm>
using namespace std;
typedef long long ll;
const int MAXN=30010;
const int MAX_INT=0x7fffffff;
const int MAXT=210;

struct node
{
    int lift;
    int steps;
    node() {lift=0;steps=0;}
};

bool vis[MAXT];
int num[MAXT];
int N,A,B;

void BFS()
{
    queue<node> q;
    node st;st.lift=A;
    st.steps=0;
    q.push(st);
    vis[A]=true;
    while(!q.empty())
    {
        node t=q.front();
        q.pop();
        if(t.lift==B) {printf("%d\n",t.steps);return;}
        node nt=t;nt.steps++;
        nt.lift=t.lift+num[t.lift];
        if(nt.lift<=N&&!vis[nt.lift])
        {
            q.push(nt);
            vis[nt.lift]=true;
        }
        nt.lift=t.lift-num[t.lift];
        if(nt.lift>=1&&!vis[nt.lift])
        {
            q.push(nt);
            vis[nt.lift]=true;
        }
    }
    printf("-1\n");
}

int main()
{
    ///freopen("sample_data.in","r",stdin);
    ///freopen("data.in","r",stdin);
    ///freopen("data.out","w",stdout);
    freopen("lift.in","r",stdin);
    freopen("lift.out","w",stdout);
    scanf("%d%d%d",&N,&A,&B);
    memset(vis,false,sizeof(vis));
    memset(num,0,sizeof(num));
    for(int i=1;i<=N;i++) scanf("%d",&num[i]);
    BFS();
    return 0;
}