SPCU  Gopu and Validity of Arrangement
N persons are standing in a line. Height of each person is between 1 and N and height of each person is distinct.
You are given an array A where A[i] denotes how many persons are there before the i_th person having heights greater than the height of the ith person. For a person i, all the persons from 1 to i  1 are considered to be before him. eg, For person 2, person 1 is considered before him.
You have to find out whether this array can be valid for some arrangement of persons. If you can uniquely do so then output "YES" Otherwise output "NO".
Input
First line contains T : number of test cases. (1 <= T <= 20).
For each test First line contains an integer n. (1 <= N <= 10^5)
Next line contains n space seperated integers denoting A[i]. (0 <= A[i] <= N)
Output
For each test case, output "YES" or "NO" according to answer.
Example
Input: 2
2
0 1
2
1 1
Output: YES
NO
Explanation
For the first test case, [2, 1] is a valid case, First person has height 2, second person has height 1.
For the second test case, no valid test case exists.
hide comments
wolfie10:
20190517 20:48:58
the logic is fairly simple and straightforward..test cases are deceptive.. :P 

silentknight16:
20190218 18:47:04
Tricky ;) 

be1035016:
20180118 16:32:41
easy 1 

kotal_kahn:
20170722 17:47:39
why it is showing the wrong answer even though my logic is correct


Shivam Gupta:
20170314 12:29:13
Don't think too much, its a trick question 

gajalchouhan:
20170308 09:03:15
please anyone can give me some another example when the print is coming " no".


Anuj Arora:
20160817 22:27:26
Move this to tutorial 

siddharth_0196:
20160617 12:04:19
One of the easiest question I have ever solved! :P :D 

utkarsh538:
20160413 18:34:15
easy question,just find the logic. 

dwij28:
20151227 11:49:28
Its amazing how a matter of time impacts your performance in coding. 3 months ago, I got 56 WA's on this, and today it took me 5 minutes to solve this. I am laughing at myself from 3 months ago.. :D 
Added by:  praveen123 
Date:  20140108 
Time limit:  2s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 
Resource:  IITK ACA CSE online judge 