POSTERS  Election Posters
A parliamentary election was being held in Byteland. Its enterprising and orderly citizens decided to limit the entire election campaign to a single dedicated wall, so as not to ruin the panorama with countless posters and billboards. Every politician was allowed to hang exactly one poster on the wall. All posters extend from top to bottom, but are hung at different points of the wall, and may be of different width. The wall is divided horizontally into sections, and a poster completely occupies two or more adjacent sections.
With time, some of the posters were covered (partially or completely) by those of other politicians. Knowing the location of all the posters and the order in which they were hung, determine how many posters have at least one visible section in the end.
Input
The input begins with the integer t, the number of test cases. Then t test cases follow.
Each test case begins with a line containing integer n  the number of posters (1 <= n <= 40000). Then n lines follow, the ith (1 <= i <= n) containing exactly two integers l_{i} r_{i}, denoting the numbers of the leftmost and rightmost sections covered by the ith poster (1 <= l_{i} < r_{i} <= 10^{7}). The input order corresponds to the order of hanging posters.
Output
For each test case output a line containing one integerĀ  the number of posters with visible sections.
Example
Sample input: 1 5 1 4 2 6 8 10 3 4 7 10 Sample output: 4
An illustration of the sample input is given below.
hide comments
Jannatul Ferdows Jenny:
20150630 11:21:17
Weak test cases : My ac code failed at this 


Nashir Ahmed:
20150617 09:58:52
will sqrt ( 10^7 ) * 40000 pass??


Hailo:
20150616 08:45:16
Its not necesary to compress coordinates. 

Eddy Cael:
20150427 20:48:10
Nice sweep problem. :D 

a b :
20141102 17:57:15
Last edit: 20150217 12:21:28 

maniAC:
20140806 01:07:34
Nice problem. 

Ellie And Joel:
20140613 11:44:15
what's problem with test 0th? it fail it self.


Pushkar Singh:
20140219 11:35:02
it's failing on 0th test case itself. Any idea what possibly can be 0th test case. 

amirmd76:
20131214 09:27:31
7 seconds ? :O


Haidar Abboud:
20130522 11:34:30
Comment #1 : done using an O(N log N) algorithm. Can it be solved in O(N) ?

Added by:  adrian 
Date:  20040719 
Time limit:  7s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All 
Resource:  VI Polish Collegiate Team Programming Contest (AMPPZ), 2001 