Sort Colors (LeetCode 75) | Dutch National Flag Problem | Full Solution with Visuals and Animations

Actual Problem: leetcode.com/problems/sort-co...
Chapters:
00:00 - Intro
00:40 - Problem Statement and Description
02:43 - The most obvious solution
05:23 - Solving for efficiency in-place
12:01 - Dry-run of Code
14:28 - Final Thoughts
📚 Links to topics I talk about in the video:
Sorting Techniques: • Sorting Techniques
Arrays: • Array Data Structure e...
📘 A text based explanation is available at: studyalgorithms.com
Code on Github: github.com/nikoo28/java-solut...
Test-cases on Github: github.com/nikoo28/java-solut...
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#leetcode #programming #interview

[@jameswalt2199]

YOU MADE IT THE SIMPLEST TO UNDERSTAND WITHOUT COMPLICATING THINGS!!!!! HAT'S OFF TO YOU!

[@Azeem_Idrisi]

Best solution I've seen for this problem. This channel is so underrated.

[@unanimous8510]

Man that’s the best explanation. I saw the coded solution for this problem which is same as yours but couldn’t wrap my head around it. Now I got it! Thank you!

[@sarthakgadge5223]

Thanks man this helped me a lot, loved your energy throughout the problem.

[@shwetayadav4244]

your explanations are really amazing. In fact, best so far :) Please make more videos :)

[@shabanlukyamuzi4012]

Best explanation on CZcams for the problem

[@azharsofi2854]

your teaching is next level

[@omdongare2005]

Your the best bro. The problem seems so easy with the way you explain it. Thanks again. Also this is my solution in python based on your approac

[@mayankbadika3101]

very good explanation! keep up the good work

[@vinoths7140]

Great Explanation, Thank You.

[@anayatk.007]

Thank you for providing such fantastic content

[@omsudhamsh.h]

Picture perfect mate!
Thanks.

[@dylanjara201]

Perfect explained. Ty sir!!

[@BroskiXP]

Great explanation, good work

[@moezzzz9341]

Your the best bro. The problem seems so easy with the way you explain it. Thanks again. Also this is my solution in python based on your approach
class Solution:
def sortColors(self, nums: List[int]) -> None:
"""
Do not return anything, modify nums in-place instead.
"""
start = 0
middle = 0
end = len(nums ) - 1
while middle

[@user-yh2vm8ge2u]

VERY NICE EXPLANATION WITH CLARITY . THANKS BHAIYA .

[@sithutun688]

best explanation Sir! I didn't watch the coding part before solving the problem. So I implemented it using if-else statements.After solving, I watched the last part. I found out you wrote it using switch cases. Understanding both versions make me confident in coding

[@neeeelll_]

Beautifully explained. could u please come up with topic based important questions

[@sumitraj9312]

Thank you, ploblem solved. love you
😁

[@user-wj4eg4rx4j]

Underrated!

[@apex095]

elegant solution. could you please add more questions on variety of topics like Stacks and Queues etc on your website ?

[@arnavkukreti2009]

you explain in a very good manner
thank you

[@nikoo28]

So nice of you

[@Harrish30]

Perfect!! Thanks

[@technicalguy.]

Thank you soo much ❤❤

[@everyontech2716]

great explanation

[@sarthakgupta096]

Thankyou sir your way of teaching is amazing

[@nikoo28]

It's my pleasure

[@jerronjones470]

Yay, someone I can understand

[@subee128]

Thank you

[@LokeshSharma-hm5jz]

i dont know why i developed a fear for this problem. You made it very easy. Thanks.

[@nikoo28]

I was once in the same boat as you my friend. :)

[@user-fq1nn1vc2p]

@@nikoo28 🙏🙏

[@iceyyeah]

Thanks

[@pranavshekhar2048]

Great explaination! But I noticed one thing, in the first example, first swap is wrong as middle was at 0, so swap between start and middle should take place and start and middle should move and not between middle and end i.e 0 and 2 what you did because middle was not at 2.

[@user-un9ri4vt7l]

sir, I actually used in-built sort function, in leetcode ie. sort(nums.begin(),nums.end()), and it said said, u beat 100% users with c++. Can we do this or not???

[@nikoo28]

You can, but your interviewer and ask you to solve it without sorting.

[@iiju8212]

Bhai kaafi mast samjhaya.

[@m-bk4um]

good

[@CPS_XI]

💯❤

[@KarthikC-ju4fx]

❤

[@officialdreamplayz]

i used selection sort

[@user-ik1qr9ez2b]

why we are not incrementing mid when it is arr[mid] is 2?

[@nikoo28]

we swap it out, and put the 2 at the end. so we don't increment it. we need to see what came after the swap.

[@bhargavinaik8145]

@@nikoo28 I solved it on leetcode, i knew it would fail for some testcases and it did, I kept trying to understand what was the pattern of those test cases, your answer made understand that exact point. Thanks :)

[@SubhajitDas-mt7sn]

c++
class Solution {
public:
void sortColors(vector& nums) {
int start = 0;
int middle = 0;
int end = nums.size() - 1;
while (middle

[@shenth27]

why don't we just loop through the entire array and count the 0's and 1's in seperate variables, then loop the array again and replace number of 0, 1, 2 in that order.

[@DohaZilaoui-zq1gx]

Its just of solution of 10000000000solutions that u should keep it in your mind

[@nikoo28]

There are multiple ways to approach the problem. You want to do in the fastest way possible. It cannot get faster than a single scan

[@unemployedcse3514]

but interviewer won't be impressed by this approach 😂😂

[@nenuanenenuane6645]

// Java code to sort an array of integers
// with the help of single loop
import java.util.*;
class Geeks_For_Geeks {
// Function for Sorting the array
// using a single loop
public static int[] sortArrays(int[] arr)
{
// Finding the length of array 'arr'
int length = arr.length;
// Sorting using a single loop
for (int j = 0; j < length - 1; j++) {
// Checking the condition for two
// simultaneous elements of the array
if (arr[j] > arr[j + 1]) {
// Swapping the elements.
int temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
// updating the value of j = -1
// so after getting updated for j++
// in the loop it becomes 0 and
// the loop begins from the start.
j = -1;
}
}
}
Bro can we use this as well plz let me know

[@chessps]

more easier!!!
class Solution {
public static void sortColors(int[] nums) {
int zero = 0;
int one = 0;
int two = 0;
for (int i: nums) {
if(i==0){
zero++;
} else if (i==1) {
one++;
}else {
two++;
}
}
for (int i = 0; i < nums.length ; i++) {
if(zero!=0){
zero--;
nums[i]= 0;
} else if (one!=0) {
one--;
nums[i]= 1;
}else if(two!=0) {
two--;
nums[i]= 2;
}
}
}
}

[@kidoo1567]

But complexity?

[@ankitraj4179]

Java Solution (Beats 100 %)
class Solution {
public void sortColors(int[] nums) {
int n = nums.length ;
int[] arr = new int[3] ;
int element = 0 ;
for(int i = 0 ; i < n ; i++){
element = nums[i] ;
arr[element]++ ;
}
int count = 0 ;
int k = 0 ;
for(int i = 0 ; i 0){
nums[k] = i ;
k++ ;
count-- ;
}
}
}
}

[@hwval-zw4hy]

Why not just count zeroes and ones and refill the array in place? 😂

[@nikoo28]

You will need to iterate over the array twice. First to count all the different 0 and 1s. Next iteration will be to actually fill all the elements.
In the approach I discuss, we just do a single scan of the array.

[@hwval-zw4hy]

@@nikoo28 I like your solution. One pass is good.
Though counting involves same big O complexity and simpler approach.
I also think your solution fits better definition of in-place. E.g. if these were objects, not integers to sort: mine solution wouldn't be acceptable.