hdu1548 A strange lift(bfs 或Dijkstra最短路径)

 #include<iostream>
 #include<cstdio>
 #include<algorithm>
 #include<cstring>
 #define M 205
 #define INF 0x3f3f3f3f
 using namespace std;

 int map[M][M];
 int d[M], vis[M];
 int n;
 int b, e;

 void Dijkstra(){
    memset(d, 0x3f, sizeof(d));
    memset(vis, , sizeof(vis));
    d[b]=;
    vis[b]=;
    int root=b;
    for(int j=; j<n; ++j){
        int minLen=INF, p;
        for(int i=; i<=n; ++i){
           if(!vis[i] && d[i] > d[root] + map[root][i])
               d[i] = d[root] + map[root][i];
           if(!vis[i] && minLen>d[i]){
              p=i;
              minLen=d[i];
           }
        }
        if(minLen==INF)
           return;
        root=p;
        vis[root]=;
    }
 }

 int main(){
    while(cin>>n && n){
        cin>>b>>e;
        memset(map, 0x3f, sizeof(map));
        for(int i=; i<=n; ++i){
           int x, xx;
           cin>>x;
           map[i][i]=;// i+(-)x 表示 从第i层可以到达第 i+（-）x层
           xx=i-x;
           if(xx>=) map[i][xx]=;
           xx=i+x;
           if(xx<=n)  map[i][xx]=;
        }
        Dijkstra();
        if(d[e]==INF)
           cout<<"-1"<<endl;
        else
           cout<<d[e]<<endl;
    }
    return ;
 } 

 /*
 思路：当前电梯位置的两个方向进行搜索！
       注意：搜索时的界限, 用x表示将要到达的电梯的位置
             1. 首先是x>=1
             2. x<=n
             3. vis[x]!=0 表明bfs时候没有经过这个楼层
 */
 #include<iostream>
 #include<cstring>
 #include<cstdio>
 #include<queue>
 using namespace std;
 struct node{
    int x;
    int step;
    node(){}
    node(int x, int step){
       this->x=x;
       this->step=step;
    }
 };
 queue<node>q;
 int n, b, e;
 int f[];
 int vis[];

 bool bfs(){
     while(!q.empty())  q.pop();
     memset(vis, , sizeof(vis));
     q.push(node(b,));
     vis[b]=;
     while(!q.empty()){
         node cur=q.front();
         q.pop();
         if(cur.x==e){
             cout<<cur.step<<endl;
             return true;
         }
         int xx;
         xx=cur.x+f[cur.x];
         if(xx==e){
            cout<<cur.step+<<endl;
            return true;
         }
         if(xx<=n && !vis[xx]){
            q.push(node(xx, cur.step+));
            vis[xx]=;
         }
         xx=cur.x-f[cur.x];
         if(xx==e){
            cout<<cur.step+<<endl;
            return true;
         }
         if(xx>= && !vis[xx]){
            q.push(node(xx, cur.step+));
            vis[xx]=;
         }
     }
     return false;
 }

 int main(){
     while(cin>>n && n){
        cin>>b>>e;
        for(int i=; i<=n; ++i)
           cin>>f[i];
        if(!bfs())
           cout<<"-1"<<endl;
     }
     return ;
 }