Find missing number in an array

This video shows three techniques on how to find the missing number in an array. The techniques are based on hashing, sum formula and XOR. If you find any difficulty or have any query then do COMMENT below. PLEASE help our channel by SUBSCRIBING and LIKE our video if you found it helpful...CYA :)

[deepjyotidebnath]

Great video ! 🙌 I understand the XOR operation by this video.

[dikshakatake]

Great video ! 🙌 No need to research the best approach just watch your videos and you are good to go ! Thanks🙌🙌

[killeraloo]

mast vide thi, sare methods samajh aa gye. Thanq.

[nitin-]

that was just amazing, before this video i was doing like sorting all the element in the array and finding all the element whether if it is at correct index for not

[aaditpalande]

Thank you sir, Just one question that how can I build my mind to think for the solution in such various approaches

[Firstusee]

If the given array is sorted, then binary search can be applied ( logn) time

[divakarkumar]

Sort the array then

For(int i=0;i<n;i++)
if(arr[i]!=i+1)
printf("%d", i+1);

[iamnimish]

XORing all the elements & then XORing the numbers till n.
And then XORing both tof the obtained results.
This brings us the left out element as XOR of a no with itself is zero(like in binary).

[Cloud-]

note that xor of any number repeats every four digits. so you ca use mod to predetermine the xor of Len(nums). then to find the missing number find the xor of the nums values ONLY. finally return the xor of Len(nums).^ xor of the nums values

[rajukumar-svvj]

sir very good explain thankyou sir ji

[ashuiet]

For input int[] a = {-1, 1, 2, 3, 4, 5, 6, 7} missing Nums : 18 but it should be '0' can you suggest why I am getting .because as per the algo explain by instructor it should be pass for boundary value also :

public class MissingNumber2 {

private static int missingNumber(int[] input, int n) {

int x1 = input[0];
int x2 = 1;

for (int i = 1; i < n; i++) {
x1 = x1 ^ input[i];
}
for (int i = 2; i <= n + 1; i++) {
x2 = x2 ^ i;
}
return x1 ^ x2;

}

public static void main(String[] args) {

int[] a = { -1, 1, 2, 3, 4, 5, 6, 7 };

int n = a.length;
int missing = missingNumber(a, n);
System.out.println(" Missing Number is ::: " + missing);

}

}

[rashibansal]

what if we sort the array and then start comparing if each element is equal to its index, wherever the condition is a false return that index value.

[mujahidpasha]

Hi, have you ever come across below question?
Given a stream of timestamp and CPU utilisations we need to return the time interval where CPU utilisations was max. Ex input 2d array. [[StartTime, EndTime, cpuUtilization]]

[cb]

1 and 2 are impratical solution it wont work If negative number is present or missing number not in between. see problem 41 leet code

[FANSasFRIENDS]

Sir, kindly explain what is overflow for this case.

[dineshverma-inon]

use binary search, time complexity will be logN

[har.preet.singh.]

Can you please share the code of the third approach?

[kartikbhanderi]

n*(n+1)/2 - sum of array elements
Will also work 😄🍻

[kommunagasheshu]

As well as please explain code for the problem.

[natnaelghirma]

Sir, what about the time it takes to make the second array(the complete one)?