Missing Number

Finding the Missing Number in an Array - Problem Solution

Given an array nums containing n distinct numbers in the range [0, n], return the only number in the range that is missing from the array.

Example Usage :

Let's consider a few examples to understand how the MissingNumber method works :

Example 1 :
Input : nums = [3,0,1]
Output : 2
Explanation : n = 3 since there are 3 numbers, so all numbers are in the range [0,3]. 2 is the missing number in the range since it does not appear in nums.

Example 2:
Input : nums = [0,1]
Output : 2
Explanation : n = 2 since there are 2 numbers, so all numbers are in the range [0,2]. 2 is the missing number in the range since it does not appear in nums.

Example 3 :
Input : nums = [9,6,4,2,3,5,7,0,1]
Output : 8
Explanation : n = 9 since there are 9 numbers, so all numbers are in the range [0,9]. 8 is the missing number in the range since it does not appear in nums.

Solution Overview : 🧾

To solve this problem, we can use a simple algorithm:

1. Calculate the sum of numbers in the range [0, n] using the formula sum = ( n * ( n + 1 )) / 2.
2. Calculate the sum of numbers in the given array nums.
3. The difference between the sum of the range and the sum of the array will be the missing number.

Implementation in C# :

public class Solution
{
	public int MissingNumber(int[] nums) 
    {
        int n = nums.Length;
        int sum = (n * (n + 1)) / 2; // Sum of numbers in range [0, n]
        int arraySum = nums.Sum();   // Sum of numbers in the array
        return sum - arraySum;       // Missing number is the difference
    }
}

Conclusion : 🔄

Finding the missing number in an array is a common programming problem that can be solved efficiently using the above algorithm. By understanding the problem and the solution approach, you can improve your problem-solving skills and write more efficient code.