# Find two Missing Numbers in a Sequence of Consecutive Numbers

**Objective :** Write an algorithm to find two Missing Numbers in a Sequence of Consecutive Numbers

**Input:** Array, arrA[] with two missing numbers and Range

**Output :** Two missing numbers

**Approach:**

- Approach is very simple, Add all the given numbers say S
- Calculate sum of N numbers by formula n(n+1)/2 , say N
- Find sum of two missing numbers a+b = N-S

- Now take the product of all given numbers say P
- Now take the product of N numbers , say Np;
- Find the product of two missing numbers ab = Np-P
- Now we have a+b and ab , we can easily calculate a and b

**Example :**

Given array : {10,2,3,5,7,8,9,1}; Range : 10 N (Sum of 1 to 10 ) = 55 S (Sum of given elements ) = 45 a+b = 10------------------------------------(1) Np(Product of 1 to 10) = 3628800 P(Product of given elements) = 151200 So a*b = 24---------------------------------(2) Now we have two equations and two variables, if we solve we will get values 6 and 4.

**Complete Code:**

**Output:**

Missing numbers are :6 and 4

The example is very good, just a small bug at line 30 in the snippet, it should be (s*2) not (s*s) in the equation

diffSqr = (int)Math.sqrt((s*s)-4*product)