TOPOSORT  Topological Sorting
Sandro is a well organised person. Every day he makes a list of things which need to be done and enumerates them from 1 to n. However, some things need to be done before others. In this task you have to find out whether Sandro can solve all his duties and if so, print the correct order.
Input
In the first line you are given an integer n and m (1<=n<=10000, 1<=m<=1000000). On the next m lines there are two distinct integers x and y, (1<=x,y<=10000) describing that job x needs to be done before job y.
Output
Print "Sandro fails." if Sandro cannot complete all his duties on the list. If there is a solution print the correct ordering, the jobs to be done separated by a whitespace. If there are multiple solutions print the one, whose first number is smallest, if there are still multiple solutions, print the one whose second number is smallest, and so on.
Example 1
Input: 8 9 1 4 1 2 4 2 4 3 3 2 5 2 3 5 8 2 8 6 Output: 1 4 3 5 7 8 2 6
Example 2
Input: 2 2 1 2 2 1 Output: Sandro fails.
hide comments
masterchef2209:
20190118 16:55:53
use Kahn's algo with priority_queue. good beginner question for topo sort 

masterchef2209:
20190118 16:55:52
also don't forget '.' in cycle case output :P Last edit: 20190118 16:57:20 

suyashky:
20181227 11:20:42
learned two different methods for topological sort...good question :) 

aayush_man3:
20181219 15:15:57
Make sure you have put '.' in "Sandro fails." 

behrads_1382:
20181120 12:30:43
first number have to be smallest or second number !!!??? 

saketag007:
20181103 12:40:38
easy , AC in one go...!! 

frpartho:
20180921 22:00:56
6 4


rudrakh97:
20180626 17:45:32
*If there are multiple solutions print the one, whose first number is smallest* Use <set> instead of <vector>. Plus cin and cout works! 

techobist:
20180529 00:05:51
Its always better to use printf and scanf than to waste your whole day. 

priyankarking:
20180218 12:35:30
nice one:) 
Added by:  Josef Ziegler 
Date:  20111023 
Time limit:  0.5s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All 