UVA - 10305 - 주문 작업 (토폴로지 정렬!)

UVA - 10305
Ordering Tasks
Time Limit: 3000MS
Memory Limit: Unknown
64bit IO Format: %lld & %llu
Submit Status
Description
Problem F
Ordering Tasks
Input: standard input
Output: standard output
Time Limit: 1 second
Memory Limit: 32 MB
 
John has n tasks to do. Unfortunately, the tasks are not independent and the execution of one task is only possible if other tasks have already been executed.
Input
The input will consist of several instances of the problem. Each instance begins with a line containing two integers, 1 <= n <= 100 and m. n is the number of tasks (numbered from 1 to n) and m is the number of direct precedence relations between tasks. After this, there will be m lines with two integers i and j, representing the fact that task i must be executed before task j. An instance with n = m = 0 will finish the input.
Output
For each instance, print a line with n integers representing the tasks in a possible order of execution.
Sample Input

5 4

1 2

2 3

1 3

1 5

0 0

Sample Output

1 4 2 5 3

(The Joint Effort Contest, Problem setter: Rodrigo Malta Schmidt)
Source
Root :: Competitive Programming 3: The New Lower Bound of Programming Contests (Steven & Felix Halim) :: Graph :: Graph Traversal ::  Topological Sort
Root :: Competitive Programming 2: This increases the lower bound of Programming Contests. Again (Steven & Felix Halim) :: Graph :: Graph Traversal ::  Topological Sort
Root :: AOAPC II: Beginning Algorithm Contests (Second Edition) (Rujia Liu) :: Chapter 6. Data Structures ::  Examples
Root :: AOAPC I: Beginning Algorithm Contests (Rujia Liu) :: Volume 2. Data Structures ::  Graphs
Root :: Competitive Programming: Increasing the Lower Bound of Programming Contests (Steven & Felix Halim) :: Chapter 4. Graph :: Depth First Search ::  Topological Sort
백서 의 토폴로지 정렬!
AC 코드:

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

int flag, n, m;
int topo[110], num[110], s[110][110];

bool dfs(int site)
{
    num[site]=-1;
    for(int i=1; i<=n; i++)
        if(s[site][i]&&(num[i]<0||(!num[i]&&!dfs(i)))) return false;
    num[site]=1;
    topo[--flag]=site;
    return true;
}

bool toposort()
{
    flag=n;
    memset(num,0,sizeof(num));
    for(int i=1; i<=n; i++)
        if(!num[i]&&!dfs(i)) return false;
    return true;
}

int main()
{
    int x,y,count;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        if(!n&&!m) break;
        memset(s,0,sizeof(s));
        for(count=0; count<m; count++)
        {
            scanf("%d%d",&x,&y);
            s[x][y]=1;
        }
        if(toposort())
            for(count=0; count<n-1; count++) printf("%d ",topo[count]);
        printf("%d
",topo[count]);
    }
    return 0;
}