CodeForces - 615B Best beautiful——简单dp

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
int n, m;
ll du[maxn], dp[maxn];
vector<int> g[maxn];

void dfs(int u) {
    if (dp[u]) return;
    ll temp = 0;
    for (unsigned int i = 0; i < g[u].size(); i++) {
        int v = g[u][i];
        dfs(v);
        temp = max(temp, dp[v]);
    }
    dp[u] = temp + 1;
}

int main() {
    scanf("%d %d", &n, &m);
    int u, v;
    memset(du, 0, sizeof(du));
    for (int i = 1; i <= m; i++) {
        scanf("%d %d", &u, &v);
        if (u < v) swap(u, v);
        du[u]++; du[v]++;
        g[u].push_back(v);
    }
    memset(dp, 0, sizeof(dp));
    for (int i = 1; i <= n; i++) dfs(i);
    ll ans = 0;
    for (int i = 1; i <= n; i++) {
        ans = max(ans, dp[i] * du[i]);
    }
    printf("%lld\n", ans);
    return 0;
}