Dp/DAG.h

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• Last update: 2025-10-06 23:30:53+07:00

Depends on

• template.h

Code

#include "../template.h"


// Longest path in graph

int n, m;
vector<vector<int>> adj;
vector<int> vis, d;
stack<int> topo;

void topoSort(int u) {
    vis[u] = 1;
    for (int v : adj[u]) {
        if (vis[v]) continue;
        topoSort(v);
    }
    topo.push(u);
}

void solve() {
    cin >> n >> m;
    adj.resize(n+1);
    for (int i = 0; i < m; i++) {
        int u, v; cin >> u >> v;
        adj[u].push_back(v);
    }
    vis.resize(n+1);
    for (int i = 1; i <= n; i++) {
        if (vis[i]) continue;
        topoSort(i);
    }
    fill(all(vis), 0);
    d.resize(n+1, 0);
    while (!topo.empty()) {
        int u = topo.top(); topo.pop();
        for (int v : adj[u]) {
            d[v] = max(d[v], d[u] + 1);
        }
    }
    cout << *max_element(all(d));
}

#line 2 "template.h"

#include <bits/stdc++.h>
using namespace std;
 
#define ll long long
#define MOD (ll)(1e9+7)
#define all(x) (x).begin(),(x).end()
#define unique(x) x.erase(unique(all(x)), x.end())
#define INF32 ((1ull<<31)-1)
#define INF64 ((1ull<<63)-1)
#define inf (ll)1e18

#define vi vector<int>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define fi first
#define se second

const int mod = 998244353;

void solve();

int main(){
    ios_base::sync_with_stdio(false);cin.tie(NULL);
    // cin.exceptions(cin.failbit);
    // int t; cin >> t;
    // while(t--)
        solve();
    cerr << "\nTime run: " << 1000 * clock() / CLOCKS_PER_SEC << "ms" << '\n';
    return 0;
}
#line 2 "Dp/DAG.h"


// Longest path in graph

int n, m;
vector<vector<int>> adj;
vector<int> vis, d;
stack<int> topo;

void topoSort(int u) {
    vis[u] = 1;
    for (int v : adj[u]) {
        if (vis[v]) continue;
        topoSort(v);
    }
    topo.push(u);
}

void solve() {
    cin >> n >> m;
    adj.resize(n+1);
    for (int i = 0; i < m; i++) {
        int u, v; cin >> u >> v;
        adj[u].push_back(v);
    }
    vis.resize(n+1);
    for (int i = 1; i <= n; i++) {
        if (vis[i]) continue;
        topoSort(i);
    }
    fill(all(vis), 0);
    d.resize(n+1, 0);
    while (!topo.empty()) {
        int u = topo.top(); topo.pop();
        for (int v : adj[u]) {
            d[v] = max(d[v], d[u] + 1);
        }
    }
    cout << *max_element(all(d));
}

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