POJ 2762 going from U-V or from V to u? (Strongly connected components + topological ordering)

Title Address: POJ 2762
First, then determine whether the number of layers per layer in the topology network is 1 (I admit that if I don't know the problem in advance, I can't think of a topological sort.) ）。 Because if there is a layer of 2, then the two fork points will not be from one point to another.
The code is as follows:

#include <iostream>#include <string.h>#include <math.h>#include <queue>#include <algorithm>#include <stdlib.h>#include <map>#include <set>#include <stdio.h>using namespace STD;#define LL __int64#define PI ACOs ( -1.0)Const intMod=1e9+7;Const intinf=0x3f3f3f3f;Const Doubleeqs=1e-9;Const intmaxn= ++Ten;intHEAD[MAXN], ecnt, SCC, top, indx;intLOW[MAXN], DFN[MAXN], BELONG[MAXN], STK[MAXN], INSTACK[MAXN];structnode{intU, V, next;} edge[7000];voidAddintUintV) {edge[ecnt].v=v;        Edge[ecnt].next=head[u]; head[u]=ecnt++;}voidTarjan (intu) {low[u]=dfn[u]=++indx; instack[u]=1; Stk[++top]=u; for(inti=head[u];i!=-1; i=edge[i].next) {intV=EDGE[I].V;if(!dfn[v])                        {Tarjan (v);                Low[u]=min (Low[u],low[v]); }Else if(Instack[v])                {low[u]=min (low[u],dfn[v]); }        }if(Low[u]==dfn[u]) {scc++; while(1){intv=stk[top--];                        BELONG[V]=SCC; instack[v]=0;if(U==V) Break; }        }}voidInit () {memset(head,-1,sizeof(head));memset(DFN,0,sizeof(DFN));memset(Instack,0,sizeof(Instack)); Ecnt=top=indx=scc=0;}intHEAD1[MAXN], Ecnt1, DEG[MAXN];structnode1{intU, V, next;} edge1[7000];voidADD1 (intUintV) {edge1[ecnt1].v=v;        Edge1[ecnt1].next=head1[u]; head1[u]=ecnt1++;}BOOLTopointSCC) {intI, u, tot, M=SCC; while(m--) {tot=0; for(i=1; i<=scc;i++) {if(!deg[i])                                {tot++;                                U=i;                        deg[i]--; }                }if(tot>1)return false; for(i=head1[u];i!=-1; i=edge1[i].next) {deg[edge1[i].v]--; }        }return true;}voidInit1 () {memset(DEG,0,sizeof(deg));memset(head1,-1,sizeof(HEAD1)); ecnt1=0;}intMain () {intN, M, I, J, u, V, T, F;scanf("%d", &t); while(t--) {scanf("%d%d", &n,&m); Init (); while(m--) {scanf("%d%d", &u,&v);                Add (U,V); } for(i=1; i<=n;i++) {if(!dfn[i]) Tarjan (i); } init1 (); for(i=1; i<=n;i++) { for(j=head[i];j!=-1; j=edge[j].next) {v=edge[j].v;if(Belong[i]!=belong[v])                                        {add1 (belong[i],belong[v]); deg[belong[v]]++;//printf ("%d%d\n", Belong[i],belong[v]);}                        }                }if(Topo (SCC))puts("Yes");Else puts("No"); }return 0;}

POJ 2762 going from u to V or from V to u? (strongly connected component + topological sort)