# Program to count elements whose next element also in the array in Python

PythonServer Side ProgrammingProgramming

Suppose we have a list of numbers say nums, we have to find the number of elements x in the array, such that x + 1 also exists in the array.

So, if the input is like nums = [4, 2, 3, 3, 7, 9], then the output will be 3, because 2+1 = 3 is present, 3+1 = 4 is present and another 3 is present so total 3.

To solve this, we will follow these steps −

• c := a list containing frequencies of each elements present in nums

• dlist := a list from list of all keys of c

• for each i in dlist, do

• if c[i + 1] > 0, then

## Example

Let us see the following implementation to get better understanding

from collections import Counter
def solve(nums):
c = Counter(nums)
dlist = list(c.keys())
for i in dlist:
if c[i + 1] > 0:

nums = [4, 2, 3, 3, 7, 9]
print(solve(nums))

## Input

[4, 2, 3, 3, 7, 9]


## Output

3
Updated on 11-Oct-2021 06:57:47