C :

#include<stdio.h>
#define MAX_VERTEX_NUM 60
#define TRUE 1
#define FALSE 0  
typedef int AdjType;
typedef int Type;
typedef struct
{
    int   num;
    AdjType A[MAX_VERTEX_NUM][MAX_VERTEX_NUM]; 
}MGraph; 
void Push(int S[],int *n,int e)  
{  
   S[(*n)++]=e;        
}  
Type Pop(int S[],int *n)  
{  
   int e=S[--(*n)];    
   return e;     
}  
Type Empty(int S[],int *n)  
{  
   if(!*n)  
       return TRUE;
   else  
       return FALSE;      
}   
void TopologicalSort(MGraph *G)
{
   char indegree[MAX_VERTEX_NUM]={0};  
   int order[MAX_VERTEX_NUM]={0};  
   int k=0,count=0,n=0; 
   int S[G->num];   
   for(int i=0;i<G->num;i++)
   {   
       S[i]=-1;
   }      
   for(int j=0;j<G->num;j++)
   {  
       for(int i=0;i<G->num;i++)  
          indegree[j]=indegree[j]+G->A[i][j];  
       if(!(indegree[j]))  
          Push(S,&n,j); 
   } 
   while(!(Empty(S,&n)))  
   {    
      int top=Pop(S,&n);  
      order[k++]=top;   
      count++;  
      for(int i=0;i<G->num;i++)
      {  
          if((indegree[i]==1)&&(G->A[top][i]==1))  
             Push(S,&n,i);  
             indegree[i]=indegree[i]-G->A[top][i];
      }   
  }  
  if(count<G->num)
  {   
      printf("ERROR\n");
  }  
  else
  {  
      for(int i=0;i<k;i++)  
         printf("%d ",order[i]);
         printf("\n");
  }              
}  
int main()  
{   
    MGraph G;
    int N;
    scanf("%d",&N);
    G.num=N;
    AdjType a[N][N];
    for(int i=0;i<N;i++)
    {  
       for(int j=0;j<N;j++)
       {  
          scanf("%d",&a[i][j]);
       } 
    }
    for(int i=0;i<N;i++)
    {  
       for(int j=0;j<N;j++)
       {  
           G.A[i][j]=a[i][j]; 
       } 
    }  
    TopologicalSort(&G);              
    return 0;  
} 

C++ :

#include <cstdio>
#include <cstdlib>
#include <stack>
#include <algorithm>
using namespace std;
const int MAXN = 50;
int mat[MAXN][MAXN], output[MAXN], indegree[MAXN];
int n, outputCnt, current;
stack<int> st;
bool TopologicalSort() {
	outputCnt = 0;
	while (!st.empty())
		st.pop();
	for (int i = 0;i < n;i++)
		indegree[i] = 0;
	for (int i = 0;i < n;i++) {
		for (int j = 0;j < n;j++) {
			if (mat[i][j])
				indegree[j]++;
		}
	}
	for (int i = 0;i < n;i++) {
		if (indegree[i] == 0) {
			st.push(i);
		}
	}
	while (!st.empty()) {
		current = st.top();
		st.pop();
		output[outputCnt++] = current;
		for (int i = 0;i < n;i++) {
			if (mat[current][i]) {
				indegree[i]--;
				if (indegree[i] == 0) {
					st.push(i);
				}
			}
		}
	}
	return (outputCnt == n);
}
int main() {
	scanf("%d", &n);
	for (int i = 0;i < n;i++) {
		for (int j = 0;j < n;j++) {
			scanf("%d", &mat[i][j]);
		}
	}
	if (TopologicalSort()) {
		for (int i = 0;i < n;i++) {
			printf("%d ", output[i]);
		}
		puts("");
	} else {
		puts("ERROR");
	}
	return 0;
}