TOPOSORT - Topological Sorting

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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.


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.


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

8 9
1 4
1 2
4 2
4 3
3 2
5 2
3 5
8 2
8 6
1 4 3 5 7 8 2 6 

Example 2

2 2
1 2
2 1
Sandro fails.

hide comments
aman005mishra: 2020-07-02 22:55:03

Kahn's with priority_queue...AC in one go!!!!

hdhimanshu: 2020-06-23 21:38:32

A good question to start with topological sorting.
first, find a cycle in DG and then just use priority_queue with vector and apply dfs from n to 1.
u will get AC.

Last edit: 2020-06-23 21:39:35
tendo: 2020-06-23 16:43:03

Even priority queue gives TLE in python. Anyone got any clue?

[NG]: The dataset is huge, ensure your I/O is up to it --> . Submit in PyPy if still in trouble.

Last edit: 2020-06-23 16:52:29
nandadeep_2001: 2020-06-13 14:00:30

Good question, we need the topological sequence which is lexicographically least

ayushpandia: 2020-06-10 00:16:24

Python Times out???

Last edit: 2020-06-10 00:17:03
ayushpandia: 2020-06-09 23:42:48

import heapq for PYTHON

auler_: 2020-05-19 12:21:18

You can solve it using dfs. You just need to sort each adjacency list in descending order and call the dfs function from n to 1.

kdjonty31: 2020-05-12 10:14:21

AC using Kahn's algorithm and priority queues.

sudipandatta: 2020-04-23 17:31:50

kahn's Algorithm. AC in one go!!

dnkm: 2020-04-16 10:34:14

c++ solution passes but when I port the same solution in Java it times out

Added by:Josef Ziegler
Time limit:0.5s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)