bzoj1589 [Usaco2008 Dec]Trick or Treat on the Farm 采集糖果

Posted 2020-06-18 HugeGun

题目链接

本来想做强连通分量的题的

然而这个题太水了。。。随便搞搞就过了

一个连通块里有且仅有一个环，从所有入度为0的点出发找出环，记录答案

然后只有一个圈但没有“把”的再来考虑

 1 #include<algorithm>
 2 #include<iostream>
 3 #include<cstdlib>
 4 #include<cstring>
 5 #include<cstdio>
 6 #include<string>
 7 #include<cmath>
 8 #include<ctime>
 9 #include<queue>
10 #include<stack>
11 #include<map>
12 #include<set>
13 #define rre(i,r,l) for(int i=(r);i>=(l);i--)
14 #define re(i,l,r) for(int i=(l);i<=(r);i++)
15 #define Clear(a,b) memset(a,b,sizeof(a))
16 #define inout(x) printf("%d",(x))
17 #define douin(x) scanf("%lf",&x)
18 #define strin(x) scanf("%s",(x))
19 #define LLin(x) scanf("%lld",&x)
20 #define op operator
21 #define CSC main
22 typedef unsigned long long ULL;
23 typedef const int cint;
24 typedef long long LL;
25 using namespace std;
26 void inin(int &ret)
27 {
28     ret=0;int f=0;char ch=getchar();
29     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=1;ch=getchar();}
30     while(ch>=‘0‘&&ch<=‘9‘)ret*=10,ret+=ch-‘0‘,ch=getchar();
31     ret=f?-ret:ret;
32 }
33 int n,next[100010],du[100010],dfn[100010],dis[100010],sta[100010],top;
34 int main()
35 {
36     inin(n);
37     re(i,1,n)inin(next[i]),du[next[i]]++;
38     re(i,1,n)if(!du[i])
39     {
40         int x=i;
41         dfn[x]=1;sta[++top]=x;
42         while(1)
43         {
44             if(dis[next[x]])
45             {
46                 int temp=0;
47                 while(top)dis[sta[top--]]=++temp+dis[next[x]];
48                 break;
49             }
50             if(dfn[next[x]])break;
51             dfn[next[x]]=dfn[x]+1,x=next[x],sta[++top]=x;
52         }
53         if(top)
54         {
55             int huan=dfn[x]-dfn[next[x]]+1,qi=next[x];
56             while(top)
57             {
58                 int y=sta[top--];
59                 if(dfn[y]<dfn[qi])dis[y]=dis[qi]+dfn[qi]-dfn[y];
60                 else dis[y]=huan;
61             }
62         }
63     }
64     re(i,1,n)if(!dis[i])
65     {
66         int x=i;
67         dfn[x]=1;sta[++top]=x;
68         while(!dfn[next[x]])dfn[next[x]]=dfn[x]+1,x=next[x],sta[++top]=x;
69         int huan=dfn[x]-dfn[next[x]]+1;
70         while(top)dis[sta[top--]]=huan;
71     }
72     re(i,1,n)printf("%d\n",dis[i]);
73      return 0;
74 }