UVa 10305 给任务排序

https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1246

题意就是最普通的拓扑排序，输出可能的排序结果。

#include<iostream>
#include<cstring>
using namespace std;
const int maxn = 1000;

int n, m, cuv[maxn][maxn], c[maxn], topo[maxn], t;

bool dfs(int u)
{
    c[u] = -1; 
    for (int v = 1; v<=n; v++) if (cuv[u][v])
    {
        if (c[v]<0) return false;  //存在有向环。 
        else if (!c[v] && !dfs(v)) return false;
    }
    c[u] = 1; topo[--t] = u;
    return true;
}

bool toposort()
{
    t = n;
    memset(c, 0, sizeof(c));
    for (int u = 1; u <= n; u++) if (!c[u])
    if (!dfs(u)) return false;
    return true;
}

int main()
{
    while (cin >> n >> m && n)
    {
        memset(cuv, 0, sizeof(cuv));
        for (int i = 1; i <= m; i++)
        {
            int u, v;
            cin >> u >> v;
            cuv[u][v] = 1;
        }
        if (toposort())
        {
            for (int i = 0; i < n - 1; i++)
                cout << topo[i] << " ";
            cout << topo[n - 1] << endl;
        }
        else
            printf("No
");
    }
    return 0;
}

2016-12-11   10:42:03