1651. Shortest Subchain(bfs)
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］）
1 #include <iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<algorithm> 5 #include<stdlib.h> 6 #include<queue> 7 #include<vector> 8 using namespace std; 9 #define N 10010 10 #define INF 0xfffffff 11 vector<int>ed[N]; 12 vector<int>::iterator it; 13 int vis[N*10],pa[N*10],a[N*10],o[N*10],f[N*10]; 14 int n,ff[N*10]; 15 struct node 16 { 17 int x,num; 18 }; 19 void bfs(int s,int e) 20 { 21 int i,oo,minz = INF; 22 queue<node>q; 23 node st,te; 24 st.x = s; 25 st.num = 0; 26 pa[s] = s; 27 q.push(st); 28 while(!q.empty()) 29 { 30 te = q.front(); 31 int u = te.x; 32 q.pop(); 33 if(te.num>minz) 34 continue; 35 if(a[u]==e) 36 { 37 minz = te.num; 38 oo = u; 39 continue; 40 } 41 if(ff[u]&&!vis[ff[u]]) 42 { 43 int v = ff[u]; 44 if(!vis[v]) 45 { 46 vis[v] = 1; 47 st.x = v; 48 st.num = te.num; 49 q.push(st); 50 pa[v] = pa[u]; 51 } 52 } 53 if(!vis[u+1]&&u<n) 54 { 55 vis[u+1] = 1; 56 st.x = u+1; 57 st.num = te.num+1; 58 q.push(st); 59 pa[u+1] = u; 60 } 61 } 62 int x = oo,g=1; 63 o[g++] = a[oo]; 64 while(x!=s) 65 { 66 x = pa[x]; 67 o[g++] = a[x]; 68 } 69 for(i = g-1 ; i >= 1; i--) 70 if(o[i]!=o[i+1]) 71 printf("%d ",o[i]); 72 puts(""); 73 } 74 int main() 75 { 76 int i; 77 scanf("%d",&n); 78 for(i =1; i <= n ; i++) 79 { 80 scanf("%d",&a[i]); 81 if(f[a[i]]) 82 { 83 ff[f[a[i]]] = i; 84 f[a[i]] = i; 85 } 86 else 87 f[a[i]] = i; 88 } 89 bfs(1,a[n]); 90 return 0; 91 }
