Given an array of non-duplicating numbers from 1 to n where one number is missing, find it.

Question

Aryan Kumar · Answer

o find the missing number in an array of non-duplicating numbers from 1 to n, you can use the following approach:
Calculate the sum of all the numbers from 1 to n using the formula: sum = n * (n + 1) / 2Calculate the sum of all the numbers in the arraySubtract the sum of the array from the sum of all the numbers from 1 to n. The difference will be the missing number.
Here's a sample code snippet in Java that implements this approach:
public class FindMissingNumber {
   public static int findMissing(int[] arr, int n) {
       int sum = n * (n + 1) / 2;
       int arrSum = 0;
       for (int i = 0; i andlt; arr.length; i++) {
           arrSum += arr[i];
       }
       return sum - arrSum;
   }
   public static void main(String[] args) {
       int[] arr = {1, 2, 4, 5, 6};
       int n = 6;
       int missingNumber = findMissing(arr, n);
       System.out.println("The missing number is: " + missingNumber);
   }
}
In this example, we have an array of numbers from 1 to 6, with one number missing (3). We call the
findMissing() method, passing in the array and the value of n (which is the length of the array plus one).
The findMissing() method calculates the sum of all the numbers from 1 to n using the formula
sum = n * (n + 1) / 2, then calculates the sum of the array using a loop. The missing number is then calculated by subtracting the sum of the array from the sum of all the numbers from 1 to n.

Krishnapriya Rajeev · Answer

The code given below shows how to find the missing number in a non-duplicating array of numbers:
class missingNum 
{ 
    public static void main(String[] args)
    {
        int[] nums = { 1, 2, 3, 5, 4, 8, 6};	// Declare and initialize and an integer array.
        int n = nums.length;	// Store length of the integer array
        int sum = ((n + 1) * (n + 2)) / 2;	// Sum of n numbers
        for (int i = 0; i andlt; n; i++)
            sum -= nums[i];		// Subtracts each element from sum
         System.out.println("The missing number is " + sum + ".");
    }
}
OUTPUT:
The missing number is 7.
We can obtain the missing element by subtracting the sum of all elements from the sum of first n natural numbers, where n is the largest number in the array.

Ravi Vishwakarma · Answer

class HelloWorld {and  and public static void main(String[] args) {and  and  and  and int[] array={4,3,8,7,5,2,6};and  and  and  and int missingNumber = findMissingNum(array);and  and  and  and System.out.println('Missing Number is 'and#43; missingNumber);and and  and }and  and public static int findMissingNum(int[] array) {and  and  and  and int n=array.lengthand#43;1;and  and  and  and int sumOfFirstNNums=n*(nand#43;1)/2;and  and  and  and int actualSumOfArr=0;and  and  and  and for (int i = 0; i andlt; array.length; iand#43;and#43;) {and  and  and  and  and  and actualSumOfArrand#43;=array[i];and  and  and  and }and  and  and  and return sumOfFirstNNums-actualSumOfArr;and  and }}
Output.
Missing Number is 1

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Given an array of non-duplicating numbers from 1 to n where one number is missing, find it.

Mukul Goenka

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