Bzoj1654 [usaco2006 Jan] The cow prom

Source: Internet
Author: User

I can't understand the question, and the Chinese and English letters are too bad...

So orz itwiiioi is huge!

The result is finally understood: calculate the number of strongly connected components of a digraph without a single point.

Tarjan... (Board * 1 get √)

 

 1 /************************************************************** 2     Problem: 1654 3     User: rausen 4     Language: C++ 5     Result: Accepted 6     Time:32 ms 7     Memory:1476 kb 8 ****************************************************************/ 9  10 #include <cstdio>11 #include <cstring>12 #include <algorithm>13  14 using namespace std;15 const int N = 10005;16 const int M = 50005;17 struct edges{18     int next, to;19 }e[M];20 int n, m;21 int cnt, top, num, tot, ans, sz;22 int dfn[N], low[N], vis[N], s[N], first[N];23  24 inline int read(){25     int x = 0, sgn = 1;26     char ch = getchar();27     while (ch < ‘0‘ || ch > ‘9‘){28         if (ch == ‘-‘) sgn = -1;29         ch = getchar();30     }31     while (ch >= ‘0‘ && ch <= ‘9‘){32         x = x * 10 + ch - ‘0‘;33         ch = getchar();34     }35     return sgn * x;36 }37  38 inline void add_edge(int x, int y){39     e[++tot].next = first[x];40     first[x] = tot;41     e[tot].to = y;42 }43  44 void DFS(int p){45     dfn[p] = low[p] = ++cnt;46     s[++top] = p, vis[p] = 1;47     int x, y;48     for (x = first[p]; x; x = e[x].next){49         y = e[x].to;50         if (!vis[y]) DFS(y);51         if (vis[y] < 2)52             low[p] = min(low[p], low[y]);53     }54     if (dfn[p] == low[p]){55         ++num, sz = 0;56         while (s[top + 1] != p){57             y = s[top--];58             vis[y] = 2;59             ++sz;60         }61         if (sz != 1) ++ ans;62     }63 }64  65 inline void tarjan(){66     cnt = top = num = 0;67     memset(vis, sizeof(vis), 0);68     for (int i = 1; i <= n; ++i)69         if (!vis[i]) DFS(i);70 }71  72 int main(){73     n = read(), m = read();74     int x, y;75     for (int i = 1; i <= m; ++i){76         x = read(), y = read();77         add_edge(x, y);78     }79     tarjan();80     printf("%d\n", ans);81     return 0;82 }
View code


(P.s. Why is the release version slower than the non-release version... This is not scientific T)

Bzoj1654 [usaco2006 Jan] The cow prom

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.