Find missing number from array in python

python/find_missing_number.py

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+'''
+Question : We are given an array with consecutive natural numbers , with one number missing 
+           We have to return that number .
+Example : Input = a =[1,2,3,4,5,6,8,9,10]
+          output = 7
+Approach : There exists a very simple approach to this problem . But , overthinking can mess it up,
+           Sum= (n(n+1))/2 is the formula for sum of n natural numbers , if we subtract then sum of 
+           elements of the given array with this then the result will be the remaining number .
+           where , n = len(a)
+'''
+class Solution:
+    def missingNumber(self, nums: list[int]) -> int:
+         n = len(nums)
+         expected_sum = n * (n + 1) // 2
+         actual_sum = sum(nums)
+         return expected_sum - actual_sum