Minimum dictionary sequence of a topological Sequence

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We found that this question requires a minimum dictionary sequence.

Obviously, it is not advisable to locate all sequences and then sort them,

So we cannot use the common Topology Sorting method. How can we maintain the topology order each time?

Use a small root heap to maintain a point with an inbound degree of 0. The inbound level is counted during input.

{$inline on}const maxn=100010;type node=record       pos,next:longint;end;var heap,getin,head,ans:array[0..maxn] of longint;    edge:array[0..maxn*2] of node;    n,m,cnt,top:longint;    check:boolean;procedure add(u,v:longint); inline;begin    inc(cnt);    edge[cnt].pos:=v;    edge[cnt].next:=head[u];    head[u]:=cnt;end;procedure swap(var a,b:longint); inline;begin    a:=a xor b;    b:=a xor b;    a:=a xor b;end;procedure up(i:longint); inline;var j:longint;begin    j:=i>>1;    while j>0 do    begin        if heap[i]View code
 
Minimum dictionary sequence of a topological Sequence