DevFactorYT Hello Fellow HackerRanker's,
I created a video-tutorial walking through this problem and intend to walk through the rest of the problems (I am finished with most of DS on my main account).
Check out the walkthrough here: https://www.youtube.com/watch?v=hKQphShaM6g
Best Regards,
DevFactor
pablocrp_crm thx so much. i want to improve my programming skills
lochek_alon It seems like this solution is no longer working because the current program's structure seems more complex now than the one on your video. But anyway, thanks for the explanation and for the work you do.
dizmartin_gonza1 My c++ solution:
vector<int> reverseArray(vector<int> a) { int aux = 0; int n = a.size(); for (int i = 0; i < n/2; ++i) { aux = a[n-i-1]; a[n-i-1] = a[i]; a[i] = aux; } return a; }buzcuberk I'd say a much bettery solution (for c++14) is:
vector<int> reverseArray(vector<int> a) { vector<int> y; for(auto x = a.end()-1; x >= a.begin(); x--) y.push_back(*x); return y; }
i_eat_code not really a better solution. your solution requires a new y vector. so the space complexity is O(n), while the solution above did everything inplace, so its space complexity is O(1).
jjwcvca And I'd say much better is simply
vector<int> reverseArray(vector<int> a)
{
return {a.rbegin(), a.rend()};
}arpitpatel1771 just do this
reverse(a.begin(),a,end()); return a;
sathvikrijo why u typing this much.... i finished the code within a couple of lines in the function;
- reverse(a.begin(),a.en());
- return a;
that's all the finished...
buzcuberk the attempt was to show traversing backwards simply reverts it when you push back
sathvikrijo i cant understand you bro.
Kanahaiya You can follow the below link to know more.
Here is the video explaination - https://youtu.be/u_oUMtj7C3k
and you can find most of the hackerrank solutions with video explaination here- https://github.com/Java-aid/Hackerrank-Solutions
and many more needs to be addeed.
Regards,
Kanahaiya Gupta
Git Hub URL | https://github.com/Java-aid/
LIKE US | https://www.facebook.com/javaaid/
SUBSCRIBE US | https://www.youtube.com/channel/UCx1hbK753l3WhwXP5r93eYA
clivic Can anyone explain why can't we just use the following plain approach compared to these solutions?
vector<int> reverseArray(vector<int> a) { vector<int> b; for(int i = a.size()-1;i>=0;i--){ b.push_back(a[i]); } return b; }
sean_novick That was my solution, except in Java.
dtrivedi I like this one. This is how would write up. The current programming structure looks really complex and it does not have to be this way. thanks for posting here so everyone knows. I am picking up programming after several years so atleast I can tell one way or other but newbies may not. thanks again
macdhollister I'm getting a bug when trying to solve this with JavaScript. I didn't change any of the main method code, so everything from the error is pre-written.
solution.js:41 ws.write(res.join(' ') + '\n'); ^ TypeError: Cannot read property 'join' of undefined at main (solution.js:41:18) at ReadStream.<anonymous> (solution.js:20:5) at emitNone (events.js:111:20) at ReadStream.emit (events.js:208:7) at endReadableNT (_stream_readable.js:1064:12) at _combinedTickCallback (internal/process/next_tick.js:138:11) at process._tickCallback (internal/process/next_tick.js:180:9)
mkhoury87 I am getting the same error. Did you find out how to get around it?
edward_tirado I had this when I forgot to return the reversed array. Would need to see your code to help though.
evgeniy_aksyonov Same here =\
jchiguru Hey everyone, got this same error in Javascript.
Instead of console logging the reversedArray -- return it instead.
skurtov162 Exaclty. return a.reverse();
rajarshi356 Its very easy passed all the test cases
import java.io.*; import java.util.*; public class Solution { public static void main(String[] args) { /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */ int n,i,b,j; Scanner sc=new Scanner(System.in); n=sc.nextInt(); int[] a=new int[n]; for(i=0;i<n;i++){ a[i]=sc.nextInt(); } for(j=a.length-1;j>=0;j--){ System.out.print(a[j]+" "); } } }
jasonganub Looks good! To make this even faster, you should loop through n/2 items and swap a[i] with a[n-1-i].
_hemant can you show this using codes?
jasonganub I have my code submitted above in the discussion area.
My way permanently makes it reverse. If the interviewer asked to reverse the array, then this solution would not work since it does not reverse it, but it prints it in reverse. If they just want it to print in reverse, then rajarshi356's works fine.
jasonganub for i in range(0, n//2): temp = arr[i] arr[i] = arr[-1-i] arr[-1-i] = temp result = "" for i in arr: result = result + str(i) + " " print(result)
thulasiram_vall1 Don't this add more operations to the logic.
dtyagi1 n = int(raw_input().strip())
arr = map(int,raw_input().strip().split(' '))
result=""
for i in range(n):
result=result+str(arr[n-1-i])+" "print result
mohamedyousfi74 the using code donètwork it only show the secret page help plz
ashi_rais problem says to read array element from Line- 4 (size) 1 2 3 4 ( array elements are all in one line)
but in your code you are reading it like
4 (size) 1 2 3 4
need to use scanner.nextLine()
h2084772909 first intput and last output,your code is easy to understand and most userful.
ashish_pathania1 why am i using a.length-1 and not a.length
rajarshi356 Since array start from 0 index so we are using the same
dziadevich for(;n>0;) System.out.print(arr[--n] + " ");
jeya28798 is any inbuild functions available for reverse a string in java
mayank113463 no! you have to convert string into stringbuilder or stringbuffer
satishbabuoffice Single line code in JavaScript
console.log(arr.reverse().join(' '));
pminkov Nice!
alxcherepanov Nice, it seems, you forgot another 28 lines of parsing.
That's what I call one line:
#!/usr/bin/env ruby gets && (puts gets.split.reverse.join(' '))
nyos22 2 lines in python, just because of n...
input() print(" ".join(str(x) for x in reversed(list(map(int, input().strip().split())))))
csixteen You can simplify your Python code:
input() print(" ".join(input().split(" ")[::-1]))
artgromov i think you forgot about number of digits to print (N)
csixteen Not necessary. I just take whatever comes as the second input, create a list from it, reverse it and print the elements glued with a space.
KeyurPotdar [deleted]msmsinghchauhan Your code didn't work.
>> print(input()==0 or " ".join(input().split()[::-1])) 10 20 30 40 50 50
a_kamal_89 I guess that you forgot to press Enter after the first integer input.
aliciali This works too.
n = int(input()) print(*list(input().split())[::-1])
shaurya2us What language is this? (Python or C++)
KeyurPotdar [deleted]
duy_tha304 Hello I'm new to python so could you please explain the * and [::-1] in the second line,please?
msmsinghchauhan - will unpack a list.
eg:
A=[1,2,3] print(*A) 1 2 3
we use [::] to slice. refer http://pythoncentral.io/how-to-slice-listsarrays-and-tuples-in-python/
eg: If we want to get a sliced list in reverse order.
print(A[::-1]) [3, 2, 1]
duy_tha304 Okay,got it.Thank you so much
- will unpack a list.
eg:
armyindiabts can u explain why u put * beforew list?
lorentz_dll [deleted]
KeyurPotdar [deleted]an0o0nym one-liner
print(*[input().split() for _ in range(2)][1][::-1])
shaurya2us What language is this?
anirudhsingla8 python
vasanthmsvs can u xplain this plz..
jacky_xue_ds It doesn't work. No reponse output
jhrozo ## yet simplier, python has it all !! print(*arr[::-1])
rojastorrado The idea is make and understand what's happening behind scenes.. Make the algorithm.
jhrozo Ok, here is the explanation. The simple print(*arr[::-1]) is equivalent to:
output_str = "" inverse_array = arr[::-1] for element in inverse_array: output_str = output_str + " " + str(element) print(output_str)
This is why Python has it all.
dgaban lol. the challenge is to make the reverse algorithm yourself. you're still relying on just using arr[::-1] instead of actually writing that algorithm yourself.
nayak628 but it is still showing the same error before using this code Traceback (most recent call last): File "solution.py", line 31, in fptr.write(' '.join(map(str, res))) TypeError: 'NoneType' object is not iterable
gurneeshchahal09 return a[::-1]
yuki_ Not as simple as yours, but how about this?
console.log(require('fs').readFileSync('/dev/stdin', 'utf8').split('\n')[1].split(' ').reverse().join(' '));
ltrico59 [deleted]
CSharpDev One-liner in C# too:
Console.WriteLine(string.Join(" ", arr.Reverse()));
aakashjaker1999 [deleted]
vasilij_kolomie1 really? do You like Python now?
def reverseArray(a):
return a[::-1]really 8 symbols...
afshan_shokath Gives me runtime error. Everything i write gives runtime error.
rodrigzer I did the same but it throws an error.
karangale Simple Python Solution
def reverseArray(a): temp = [] size = len(a) for i in range(size-1, -1, -1): temp.append(a[i]) return temp
dedeco The Zen of Python:
for x in reversed(arr): print x,
asoback I did something similar, every time I tried to print x in the for loop I was getting a vertical output, so I made it a string.
*Edit: I copy and pasted your code, and didn't pass due to having the vertical output. Did it work for you?
This passed for me.
import sys n = int(input().strip()) arr = [int(arr_temp) for arr_temp in input().strip().split(' ')] c = "" for x in arr[::-1]: c += str(x) + " " print(c)
dedeco Yes man, worked! Please try again and let me know. Did you try here? or in your terminal?
See:
krutika_shah I do the same code but compiler shows me wrong answer... in python 2.. I think it isnt working in Python 2
jonhope3 A little more thought required, but an interesting solution:
static int[] reverseArray(int[] a) { int[] solution = new int[a.length]; for(int i=a.length-1, j=0; i>-1; i--, j++) { solution[j] = a[i]; } return solution; }
Kanahaiya Your solution is good. But still can be optimized. You can follow the
below link to know more.
Here is the video explaination - https://youtu.be/u_oUMtj7C3k
and you can find most of the hackerrank solutions with video explaination here- https://github.com/Java-aid/Hackerrank-Solutions and many more needs to be addeed.
Regards,
Kanahaiya Gupta
Git Hub URL | https://github.com/Java-aid/
LIKE US | https://www.facebook.com/javaaid/
SUBSCRIBE US | https://www.youtube.com/channel/UCx1hbK753l3WhwXP5r93eYA
jpablo_92_67 Hello everyone ,
I have a doubt about this exercise. this is my func that show the output as the example but it doesn't pass , and I don't understand why.( I completed the exercise with the help of this forum , but I am trying to understand why the answer is an array and not a string as the example.)
def reverseArray(a):
b= [str(i) for i in a] c = b[::-1] result = " ".join(c) return result
cupofchar I'm getting this issue too! I'm using Python 3 and have tried a few different approaches. Same runtime error each time despite matched actual/expected output.
ankurmadaan2787 You dont even need to create a new array, we can just manipulate the existing array and O(n) will be half.
See this implementation in C#:-
int n = a.Length; int lengthToTraverse = a.Length % 2==0?a.Length/2:a.Length/2+1; for (int i = 0; i < lengthToTraverse; i++) { int temp = a[i]; a[i] = a[n - (i + 1)]; a[n - (i + 1)] = temp; } return a;
Here i am dividing input array by 2, if its even then my for loop will traverse lesser than half, if odd then one plus. I have divided the array and will swap the index values, last one will go in first like wise...
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