Tarjan 【整理】

#include<bits/stdc++.h>
using namespace std;

class FastIO{
/* copyright (c) dgklr 2019. All rights reserved. */
    bool if_debug = 0;
    char st[70]; // stack
    int pl;
#ifdef linux
    #define putc(x) putchar_unlocked(x)
    #define getc() getchar_unlocked()
#else
    #define putc(x) putchar(x)
    #define getc() getchar()
#endif
#define endl '\n' // I don't have the authority to get this.
public:
    FastIO operator << (long long x){
        pl = 0;
        if (x == 0) putc('0');
        if (x < 0) putc('-');
        while (x != 0)
            st[++pl] = x % 10 + 48, x /= 10;
        while (pl != 0)
            putc(st[pl]), pl --;
        return (*this);
    }
    FastIO operator << (int x){
        pl = 0;
        if (x == 0) putc('0');
        if (x < 0) putc('-');
        while (x != 0)
            st[++pl] = x % 10 + 48, x /= 10;
        while (pl != 0)
            putc(st[pl]), pl --;
        return (*this);
    }
    FastIO operator << (char c){
        putc(c);
        return (*this);
    }
    FastIO operator << (string s){
        for (string::iterator it = s.begin(); it != s.end(); it ++)
            putc(*it);
    }
    FastIO operator << (char *c){
        int pl = 0;
        while (c[pl] != '\0') putc(c[pl++]);
    }
    template <typename T>
    FastIO operator << (vector <T> &a){
        putc('[');
        typedef typename vector <T> :: iterator Iter;
        if (a.begin() == a.end()) putc(']');
        else{
            (*this) << *a.begin();
            for (Iter it = ++a.begin(); it != a.end(); it ++)
                (*this) << ", " << *it;
            putc(']');
        }
    }
    template <typename T>
    FastIO operator << (set <T> &a){
        putc('[');
        typedef typename set <T> :: iterator Iter;
        if (a.begin() == a.end()) putc(']');
        else{
            (*this) << *a.begin();
            for (Iter it = ++a.begin(); it != a.end(); it ++)
                (*this) << ", " << *it;
            putc(']');
        }
    }
    template <typename S, typename T>
    FastIO operator << (map <S, T> &a){
        putc('[');
        typedef typename map <S, T> :: iterator Iter;
        if (a.begin() == a.end()) putc(']');
        else{
            (*this) << a.begin() -> first << ':' << a.begin() -> second;
            for (Iter it = ++a.begin(); it != a.end(); it ++)
            (*this) << ", " << it -> first << ':' << it -> second;
            putc(']');
        }
    }
    template <typename S, typename T>
    FastIO operator << (pair <S, T> &Pt){
        putc('<'); (*this) << Pt.first; putc(','); putc(' '); (*this) << Pt.second; putc('>');
    }
    FastIO operator >> (long long &x){
        x = 0;
        register char c;
        register int w = 1;
        while (c = getc(), c < '0' || c > '9') if (c == '-') w = -1;
        while (c >= '0' && c <= '9') x = x * 10 + c - 48, c = getc();
        return (*this);
    }
    FastIO operator >> (int &x){
        x = 0;
        register char c;
        register int w = 1;
        while (c = getc(), c < '0' || c > '9') if (c == '-') w = -1;
        while (c >= '0' && c <= '9') x = x * 10 + c - 48, c = getc();
        return (*this);
    }
    FastIO operator >> (char &c){
        c = getc();
        return (*this);
    }
}IO;

int dfn[101000];
int low[101000];
int n; int m;
vector <int> f[101000]; // edge
stack <int> stk; int pl = 0;
int vis[101000];
int ans[101000];
void dfs(int x){
    dfn[x] = low[x] = ++pl;
    stk.push(x);
    vis[x] = 1;
    for (auto i : f[x]){
        if (!dfn[i]){
            dfs(i);
            low[x] = min(low[x], low[i]);
        }
        else if (vis[i]){
            low[x] = min(low[x], dfn[i]);
        }
    }
    if (dfn[x] == low[x]){
        while (stk.top() != x){
            vis[stk.top()] = 0;
            ans[stk.top()] = x;
            stk.pop();
        }
        vis[x] = 0;
        ans[x] = x;
        stk.pop();
    }
}

int main(){
    IO >> n >> m;
    for (int i=1;i<=m;i++){
        int tp1, tp2;
        IO >> tp1 >> tp2;
        f[tp1].emplace_back(tp2);
    }
    for (int i=1;i<=n;i++)
    {
        if (dfn[i] == 0){
            dfs(i); // 缩点
        }
    }
    for (int i=1;i<=n;i++)
        cout << ans[i] << ' ';
}