UVa-10305 Ordering Tasks

#include <bits/stdc++.h>

const int maxn = 102;
using namespace std;

int G[maxn][maxn];
int n,m;
int vis[maxn];
int topo[maxn],tmpN;
bool dfs(int u)
{
    vis[u] = -1;//under visting
    for(int v = 1; v <= n; v ++)
    {
        if(G[u][v])
        {
            if(vis[v]<0)    return false;//loop
            else if(!vis[v] && !dfs(v))    return false;
        }
    }
    vis[u] = 1;
    topo[--tmpN]=u;

    return true;
}

bool toposort()
{
    tmpN = n;
    for(int u = 1; u <= n; u ++)
    {
        if(!vis[u])
            if(!dfs(u))
                return false;
    }
    return true;
}

void solve()
{
    if(toposort())
    {
        for(int i = 0; i < n; i ++)
            cout << topo[i] << " ";
        cout << endl;
    }
}

int main()
{
    while(cin >> n >> m)
    {
        memset(G,0,sizeof(G));
        memset(vis,0,sizeof(vis));
        while(m --)
        {
            int tmp1,tmp2;
            cin >> tmp1 >> tmp2;
            G[tmp1][tmp2] = 1;
        }
        solve();
    }
    return 0;
}