2252 줄세우기

#include <stdio.h>
#include <queue>
#include <vector>
 
using namespace std;
 
int indegree[33000] = { 0 };
vector<vector<int> > adj(33000);
queue<int> q;
 
int main() {
    int n, m;
    scanf("%d %d", &n, &m);
 
    for (int i = 0; i < m; i++) {
        int a, b;
        scanf("%d %d", &a, &b);
 
        indegree[b]++;
        adj[a].push_back(b);
    }
 
    for (int i = 1; i <= n; i++)
        if (indegree[i] == 0)
            q.push(i);
 
    while (q.empty() == false) {
        int x = q.front();
        printf("%d ", x);
        q.pop();
 
        for (int i = 0; i < adj[x].size(); i++) {
            indegree[adj[x][i]]--;
 
            if (indegree[adj[x][i]] == 0)
                q.push(adj[x][i]);
        }        
    }            
}