1 #include<iostream> 2 #include<cstdio> 3 #include<algorithm> 4 #include<cstring> 5 #define M 205 6 #define INF 0x3f3f3f3f 7 using namespace std; 8 9 int map[M][M]; 10 int d[M], vis[M]; 11 int n; 12 int b, e; 13 14 void Dijkstra(){ 15 memset(d, 0x3f, sizeof(d)); 16 memset(vis, 0, sizeof(vis)); 17 d[b]=0; 18 vis[b]=1; 19 int root=b; 20 for(int j=1; j<n; ++j){ 21 int minLen=INF, p; 22 for(int i=1; i<=n; ++i){ 23 if(!vis[i] && d[i] > d[root] + map[root][i]) 24 d[i] = d[root] + map[root][i]; 25 if(!vis[i] && minLen>d[i]){ 26 p=i; 27 minLen=d[i]; 28 } 29 } 30 if(minLen==INF) 31 return; 32 root=p; 33 vis[root]=1; 34 } 35 } 36 37 int main(){ 38 while(cin>>n && n){ 39 cin>>b>>e; 40 memset(map, 0x3f, sizeof(map)); 41 for(int i=1; i<=n; ++i){ 42 int x, xx; 43 cin>>x; 44 map[i][i]=0;// i+(-)x 表示 从第i层可以到达第 i+（-）x层 45 xx=i-x; 46 if(xx>=1) map[i][xx]=1; 47 xx=i+x; 48 if(xx<=n) map[i][xx]=1; 49 } 50 Dijkstra(); 51 if(d[e]==INF) 52 cout<<"-1"<<endl; 53 else 54 cout<<d[e]<<endl; 55 } 56 return 0; 57 }
1 /* 2 思路：当前电梯位置的两个方向进行搜索！ 3 注意：搜索时的界限, 用x表示将要到达的电梯的位置 4 1. 首先是x>=1 5 2. x<=n 6 3. vis[x]!=0 表明bfs时候没有经过这个楼层 7 */ 8 #include<iostream> 9 #include<cstring> 10 #include<cstdio> 11 #include<queue> 12 using namespace std; 13 struct node{ 14 int x; 15 int step; 16 node(){} 17 node(int x, int step){ 18 this->x=x; 19 this->step=step; 20 } 21 }; 22 queue<node>q; 23 int n, b, e; 24 int f[205]; 25 int vis[205]; 26 27 bool bfs(){ 28 while(!q.empty()) q.pop(); 29 memset(vis, 0, sizeof(vis)); 30 q.push(node(b,0)); 31 vis[b]=1; 32 while(!q.empty()){ 33 node cur=q.front(); 34 q.pop(); 35 if(cur.x==e){ 36 cout<<cur.step<<endl; 37 return true; 38 } 39 int xx; 40 xx=cur.x+f[cur.x]; 41 if(xx==e){ 42 cout<<cur.step+1<<endl; 43 return true; 44 } 45 if(xx<=n && !vis[xx]){ 46 q.push(node(xx, cur.step+1)); 47 vis[xx]=1; 48 } 49 xx=cur.x-f[cur.x]; 50 if(xx==e){ 51 cout<<cur.step+1<<endl; 52 return true; 53 } 54 if(xx>=1 && !vis[xx]){ 55 q.push(node(xx, cur.step+1)); 56 vis[xx]=1; 57 } 58 } 59 return false; 60 } 61 62 int main(){ 63 while(cin>>n && n){ 64 cin>>b>>e; 65 for(int i=1; i<=n; ++i) 66 cin>>f[i]; 67 if(!bfs()) 68 cout<<"-1"<<endl; 69 } 70 return 0; 71 }