Find the Missing Number

Easy
Array Math Algorithm
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Problem Description

Find the Missing Number

Given an array of size 'n' containing n-1 distinct numbers in the range of 1 to n. Find the missing number.

Write a function that takes an array of integers as an input and returns the missing number.

Example 1: 

Input: [1, 2, 4, 5, 6]
Output: 3

Example 2: 

Input: [2, 3, 1, 5]
Output: 4

Constraints:

  • The array contains distinct integers in the range 1 to n.
  • The size of the array is n-1.

Hints

Think about the formula for the sum of the first n natural numbers.

Consider how you can use this formula to find the missing number.

Solution