1651. Shortest Subchain(bfs)

１６５１

终于Ａ了　

看这题容易想到最短路　看到错的很多　还特意注意了好几处

后来发现　必须按给出的顺序出边　想了想　这不就是ＢＦＳ　

然后就是各种细节　ｉ－＞ｉ＋１ｏｒｉ－＞ｊ（ａ［ｉ］＝＝ａ［ｊ］）

　

 #include <iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<stdlib.h>
 #include<queue>
 #include<vector>
 using namespace std;
 #define N 10010
 #define INF 0xfffffff
 vector<int>ed[N];
 vector<int>::iterator it;
 int vis[N*],pa[N*],a[N*],o[N*],f[N*];
 int n,ff[N*];
 struct node
 {
     int x,num;
 };
 void bfs(int s,int e)
 {
     int i,oo,minz = INF;
     queue<node>q;
     node st,te;
     st.x = s;
     st.num = ;
     pa[s] = s;
     q.push(st);
     while(!q.empty())
     {
         te = q.front();
         int u = te.x;
         q.pop();
         if(te.num>minz)
         continue;
         if(a[u]==e)
         {
             minz = te.num;
             oo = u;
             continue;
         }
         if(ff[u]&&!vis[ff[u]])
         {
             int v = ff[u];
             if(!vis[v])
             {
                 vis[v] = ;
                 st.x = v;
                 st.num = te.num;
                 q.push(st);
                 pa[v] = pa[u];
             }
         }
         if(!vis[u+]&&u<n)
         {
             vis[u+] = ;
             st.x = u+;
             st.num = te.num+;
             q.push(st);
             pa[u+] = u;
         }
     }
     int x = oo,g=;
     o[g++] = a[oo];
     while(x!=s)
     {
         x = pa[x];
         o[g++] = a[x];
     }
     for(i = g- ; i >= ; i--)
     if(o[i]!=o[i+])
     printf("%d ",o[i]);
     puts("");
 }
 int main()
 {
     int i;
     scanf("%d",&n);
     for(i =; i <= n ; i++)
     {
         scanf("%d",&a[i]);
         if(f[a[i]])
         {
             ff[f[a[i]]] = i;
             f[a[i]] = i;
         }
         else
         f[a[i]] = i;
     }
     bfs(,a[n]);
     return ;
 }