题目详见http://7xjob4.com1.z0.glb.clouddn.com/3f644de6844d64706eb36baa3a0c27b0

这题是普通的拓扑排序，要把每一层的都保存下来。

#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<string>
#include<algorithm>
using namespace std;
typedef long long ll;
#define inf 99999999
#define pi acos(-1.0)
#define MOD 1000000007
struct edge{int to,next;
}e[2*20050];
int first[5050],du[5050];
int q[1111111];
int n,m;
int ceng[5050][5050],num[5050],deep[5050],cengshu,sum[5050];void topu()
{int i,j;int front,rear;front=1;rear=0;memset(num,0,sizeof(num));memset(deep,0,sizeof(deep));for(i=1;i<=n;i++){if(!du[i]){rear++;q[rear]=i;deep[i]=1;}}int x,y,xx,yy;cengshu=1;while(front<=rear){x=q[front];front++;cengshu=max(cengshu,deep[x]);num[cengshu]++;ceng[cengshu ][num[cengshu] ]=x;for(i=first[x];i!=-1;i=e[i].next){int v=e[i].to;du[v]--;if(!du[v]){rear++;q[rear]=v;deep[v]=deep[x]+1;}}}sum[0]=0;for(i=1;i<=cengshu;i++){sum[i]=sum[i-1]+num[i];}
}int main()
{int i,j,l,r,tot,c,d;while(scanf("%d%d%d%d",&l,&r,&n,&m)!=EOF){memset(first,-1,sizeof(first));memset(du,0,sizeof(du));tot=0;for(i=1;i<=m;i++){scanf("%d%d",&c,&d);c++;d++;du[d]++;tot++;e[tot].next=first[c];e[tot].to=d;first[c]=tot;}topu();int num1,num2,num3;for(i=1;i<=cengshu;i++){if(sum[i]>l)break;}i--;num1=sum[i];for(i=1;i<=cengshu;i++){if(sum[i]>r)break;}i--;num2=sum[i];for(i=1;i<=cengshu;i++){if(sum[i]>=r)break;}if(i>=cengshu)num3=0;else num3=sum[cengshu]-sum[i];printf("%d\n%d\n%d\n",num1,num2,num3);}return 0;
}