ALTSEQ  Alternating Sequences
Given an array a of N integers a1, a2, a3, ... aN you have to find the longest alternating subsequence of this array .
An alternating sequence b1, b2 ... bk, k>=1 is a sequence that has the 2 following properties:
1.b1<b2<b3<.....<bk
2. The signs alternate between adjacent elements, i.e, if b1 > 0 then b2<0, b3 >0 and so on. Alternatively, if b1<0, then b2>0, b3<0 and so on.
A sub sequence of array a is a sequence obtained by dropping some elements of the array a.
Here is the formal definition.
It is guaranteed that the array a contains no element equal to 0.
Constraints
1<=N<=5000 ai<=10^9, ai not equal to 0.
Input
The first line contains a single integer N, denoting the size of the array. The next line contains N integers , denoting the array a.
Output
Print a single integer  the length of the longest alternating subsequence.
Example
Input: 8 1 2 2 3 5 7 8 10 Output: 5
Explaination
One of the longest alternating subsequence is 1 2 5 7 10
hide comments
ks1999:
20190411 21:44:50
For everyone who is getting WA, if you are checking if one is negative and other positive with a*b < 0 that is wrong, it is going to overflow, and if says WA at 15th case it doesnt mean that you are wrong at that case, it just means that compiler or what ever reads every test case and after that he evaluate your code. 

mranderson:
20190405 13:00:01
to check that two elements have opposite signs, doing the product between them can lead to overflow error even with long long 

sai_chavali:
20190304 10:00:00
I don't why this problem is giving TLE in python but same logic accepted in C 

anshuman16423:
20180923 06:42:34
AC in one go!!


codefield:
20180705 19:10:35
if gets stuck on test case 15, check 2 test cases:


liman98:
20180625 01:27:52
lol I missed AC like 56 times because of wrong bracket combos in if statement XD 

soham_12345:
20180613 11:32:00
My 50th Last edit: 20180613 11:33:21 

aman_sachin200:
20180613 09:59:55
Easy One!! 

dsri_99:
20180606 08:04:13
wasted a lot of time at test case 15. Else it's a simple dp problem


akk007:
20180525 11:00:08
if stuck on test case #15 :

Added by:  Beer hu !! 
Date:  20160701 
Time limit:  1s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 GOSU JSMONKEY 
Resource:  Hackerrank 