[UVa] 10305 Ordering Tasks.cpp

#include <cstdio>
#include <vector>
using namespace std;
void DFS(int n, int visit[], vector<int> toNode[], vector<int> &ans);
int main()
{
    int N, M, a, b;
    while (scanf("%d %d", &N, &M) && (N || M)) {
        vector<int> toNode[101];
        vector<int> ans;
        bool connect[101] = {0};
        int visit[101] = {0};
        while (M--) {
            scanf("%d %d", &a, &b);
            toNode[a].push_back(b);
            connect[b] = 1;
        }
        for (int i = 1; i <= N; ++i) {
            if (!connect[i])
                DFS(i ,visit, toNode, ans);
        }
        for (auto iter = ans.end() - 1; iter != ans.begin(); --iter)
            printf("%d ", *iter);
        printf("%d\n", *ans.begin());
    }
}
void DFS(int n, int visit[],vector<int> toNode[], vector<int> &ans)
{
    if (visit[n] == 1) return;
    visit[n] = 1;

    for (int nxt : toNode[n]) {
        if (visit[nxt] != 2)
            DFS(nxt, visit, toNode, ans);
    }
    visit[n] = 2;
    ans.push_back(n);
}