dfs

#include <iostream>
#include <cstring>

using namespace std;

const int N = 510;

int g[N][N];
bool st[N];

struct Node
{
    int id;
    Node* next;
    Node(int _id) : id(_id), next(NULL) {}
}* head[N];
void add(int a, int b)
{
    Node* p = new Node(b);
    p->next = head[a];
    head[a] = p;
    “············”
    g[a][b] = 1;

}

void dfs(int u)  //邻接表
{
    st[u] = true;
    cout << u << ' ';

    for (Node* p = head[u]; p; p = p->next)
        if (!st[p->id])
            dfs(p->id);
}

void dfs2(int u)  //邻接矩阵
{
    st[u] = true;
    cout<<u<<' ';
    for(int i=u; i<=n; i++)
    {
        if(g[u][i]==1&&st[i]==false)
           dfs(i);
    }
}
int main()
{
    int n, m;
    cin >> n >> m;
    while (m -- )
    {
        int a, b;
        cin >> a >> b;
        add(a, b);
        // g[a][b] = w;
    }

    for (int i = 1; i <= n; i ++)
        if (!st[i])
            dfs(i);

    return 0;
}