• POJ 1236 Network of Schools


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    AcWing 367 学校网络洛谷 P2812 校园网络 加强版

    #include <iostream>
    #include <cstdio>
    #include <cstring>
    #include <algorithm>
    #include <stack>
    
    using namespace std;
    typedef long long ll;
    typedef pair<int, int> p;
    const int maxn(1e4 + 10);
    const int maxm(5e6 + 10);
    int ecnt, head[maxn];
    int tim, dfn[maxn], low[maxn];
    int scnt, scc[maxn], siz[maxn];
    int indeg[maxn], outdeg[maxn];
    bool vis[maxn];
    stack<int> st;
    
    struct edge {
        int to, nxt;
    } edges[maxm];
    
    template<typename T>
    inline const T read()
    {
        T x = 0, f = 1;
        char ch = getchar();
        while (ch < '0' || ch > '9') {
            if (ch == '-') f = -1;
            ch = getchar();
        }
        while (ch >= '0' && ch <= '9') {
            x = (x << 3) + (x << 1) + ch - '0';
            ch = getchar();
        }
        return x * f;
    }
    
    template<typename T>
    inline void write(T x, bool ln)
    {
        if (x < 0) {
            putchar('-');
            x = -x;
        }
        if (x > 9) write(x / 10, false);
        putchar(x % 10 + '0');
        if (ln) putchar(10);
    }
    
    void addEdge(int u, int v)
    {
        edges[ecnt].to = v;
        edges[ecnt].nxt = head[u];
        head[u] = ecnt++;
    }
    
    void tarjan(int u)
    {
        dfn[u] = low[u] = ++tim;
        vis[u] = true;
        st.push(u);
        for (int i = head[u]; compl i; i = edges[i].nxt) {
            int v = edges[i].to;
            if (not dfn[v]) {
                tarjan(v);
                low[u] = min(low[u], low[v]);
            } else if (vis[v]) {
                low[u] = min(low[u], dfn[v]);
            }
        }
        if (dfn[u] == low[u]) {
            ++scnt;
            int v = 0;
            do {
                v = st.top();
                st.pop();
                vis[v] = false;
                scc[v] = scnt;
                ++siz[scnt];
            } while (v not_eq u);
        }
    }
    
    int main()
    {
    #ifdef ONLINE_JUDGE
    #else
        freopen("input.txt", "r", stdin);
    #endif
        ios::sync_with_stdio(false);
        memset(head, -1, sizeof head);
        int n = read<int>();
        for (int u = 1; u <= n; ++u) {
            int v = 0;
            while ((v = read<int>())) {
                addEdge(u, v);
            }
        }
        for (int i = 1; i <= n; ++i) {
            if (not dfn[i]) {
                tarjan(i);
            }
        }
        for (int u = 1; u <= n; ++u) {
            for (int i = head[u]; compl i; i = edges[i].nxt) {
                int v = edges[i].to;
                int a = scc[u], b = scc[v];
                if (a not_eq b) {
                    ++indeg[b];
                    ++outdeg[a];
                }
            }
        }
        int hcnt = 0, tcnt = 0;
        for (int i = 1; i <= scnt; ++i) {
            if (not indeg[i]) {
                ++hcnt;
            }
            if (not outdeg[i]) {
                ++tcnt;
            }
        }
        write(hcnt, true);
        write(scnt > 1 ? max(hcnt, tcnt) : 0, true);
        return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/singularity2u/p/13899592.html
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