POJ 1236 Network of Schools

传送门

#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;
}