### The input “nums” is supposed to be an array of unique integers ranging from 1 to nums.length. However there is a mistake: one of the number in the array is duplicated, which means another number is missing. Find and return the sum of the duplicated number and the missing number. Example: In the array [4, 3, 3, 1], 3 is present twice and 2 is missing so 3 + 2 = 5 should be returned.

Points to remember before solving

• The range of the array should be 1 to the length of the array. That means if the length of the array is 5 then the elements will be [1, 2, 3, 4, 5].
• One number is duplicated with another number.  Example: [2, 2, 3, 4, 5]
• Find the missing number and also duplicated number.

Lets start…

Input:  [1, 2, 3, 4, 5, 5, 7]

Output: 11

Reason: Missing value in the array is 6 and the duplicate value in the array is 5. So the sum of these two numbers will be 11

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

Output: 3

Reason: Missing value is 1 and duplicated value is 2 in the array. So 1 + 2 = 3.

JavaScript Code:

``````// JavaScript Code

function sum_missing_duplicated(arr) {
// sort the array first
let sorted = arr.sort((a, b) => a - b)
// declaring two variables
let missing, repeated

// loop to iterate the array
for (let i = 0; i < sorted.length; i++) {
let item = sorted[i];
if( !arr.includes(i + 1)){
missing = i + 1
}
for (let j = i; j < sorted.length; j++) {
if (item === sorted[j + 1]) repeated = sorted[i];
}
}
return missing + repeated
}

// --------------------------

let myArray = [1, 2, 3, 3, 5, 6];

Output:

Python Code:

``````// Python Code

def sum_missing_duplicated(arr):
arr.sort() # sort the list first
missing = 0
repeated = 0

# Iterate from first index to last index
for i in range(0, len(arr)):
item = arr[i]
isexist = False

if not i + 1 in arr:
missing = i + 1

for j in range(i, len(arr) - 1):
if item == arr[j + 1]:
repeated = arr[i]

return missing + repeated

# -------------------------

mylist = [1, 2, 2, 4, 5]

Output:

`Answer is: 5`

You can comment your own code in the comment box…

## One Reply to “Find and return the sum of missing and duplicate number – Easy Code”

1. PythonNOOB says:

GOOD SOLUTION