判断拓扑序列
作者:
ysc
,
2021-07-28 10:51:49
,
所有人可见
,
阅读 244
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int N = 1e5+10;
int h[N], e[N], ne[N], idx;
int d[N];
int q[N];
int n, m;
void add(int a, int b)
{
e[idx] = b, ne[idx] = h[a], h[a] = idx ++;
}
bool topsort()
{
int hh = 0, tt = -1;
for ( int i = 1; i <= n; i ++ )
if ( !d[i] ) q[++ tt] = i;
while ( hh <= tt )
{
int t = q[hh ++];
for ( int i = h[t]; i != -1; i = ne[i] )
{
int j = e[i];
if ( -- d[j] == 0 ) q[++ tt] = j;
}
}
return tt == n - 1;
}
int main()
{
memset(h, -1, sizeof h);
cin >> n >> m;
while ( m -- )
{
int a, b;
cin >> a >> b;
add(a, b);
d[b] ++;
}
if ( topsort() )
{
for ( int i = 0; i < n; i ++ ) cout << q[i] << ' ';
puts("");
}
else puts("-1");
return 0;
}