topo排序

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#define MAX_VERTEX_NUM 20
using namespace std;
typedef struct
{
    int arc[MAX_VERTEX_NUM+10][MAX_VERTEX_NUM+10];
    int vexnum,arcnum;
} Mgraph;
int num[MAX_VERTEX_NUM+10];
void init(Mgraph *G)
{
    memset(G->arc,0,sizeof(G->arc));
    memset(num,0,sizeof(num));
    char ch;
    scanf("%d,%d",&G->vexnum,&G->arcnum);
    for(int i=1; i<=G->arcnum; i++)
    {
        int a,b;
        scanf("%d,%d",&a,&b);
        if(!G->arc[a][b])
        {
            G->arc[a][b]=1;
            num[b]++;
        }
    }
}
void topo(Mgraph &G)
{
    int T=G.vexnum;
    while(T--)
    {
        int sub=0,i,j;
        for(i=G.vexnum-1; i>=0; i--)//题目要求栈存储入入度为0的点，这里要逆序遍历
        {
            if(!num[i])
            {
                sub=i;
                break;
            }
        }
        num[sub]--;
        if(i==-1)
            break;
        else
            cout<<sub<<" ";
        for(j=0; j<G.vexnum; j++)
        {
            if(G.arc[sub][j]!=0)
                num[j]--;
        }
    }
}
int main()
{
    Mgraph G;
    init(&G);
    topo(G);
}