Lonely integer
This is an exercise taken from HackerRank with a couple of changes made trying to enrich it.
Given an array of integers, where all elements but one occur twice, find the unique element.
Example
a=[1,2,3,4,3,2,1]
The unique element is 4.
Function Description
Complete the lonely_integer function in the editor below.
lonely_integer has the following parameter(s):
values: an array of integers
Returns
int: the element that occurs only once
Input Format
The first line contains a single integer, N, the number of integers in the array.
The second line contains n space-separated integers that describe the values in a.
Constraints
1) N>=1, N small than 100
2) N is an odd number
3) a[i]>=0, a[i]<=100
It is guaranteed that there is one unique element.
My solution
#!/bin/python3
import math
import os
import random
import re
import sys
#
# Complete the 'lonely_integer' function below.
#
# The function is expected to return an INTEGER.
# The function accepts INTEGER_ARRAY a as parameter.
#
def lonely_integer(values:list)->int:
'''
Find the one unique element.
Find one unique element between n repeated elements.
Parameters
----------
values : list of int
len(values) is an odd number.
Return
------
i: int.
Examples
--------
values = [1,2,3,2,1]
i = 3.
values = [2,2,1,1,3]
i = 3.
'''
if (len(values)<1>=100):
raise ValueError('Values must contain odd number of elements')
if len(values) % 2 == 0:
raise ValueError('Odd number of elements is required')
for i in values:
if (i>0 and i<=100):
if values.count(i) == 1:
return i
else: raise ValueError('Values out of range:')
if __name__ == '__main__':
A=[1,2,3,2,1]
result = lonely_integer(A)
print(result)Explanation
1) Taking in account the constraints
First constraint: N>=1, N<100>
if (len(values)<1>=100):
raise ValueError('Values must contain odd number of elements')Second constraint: N must be an odd number:
if len(values) % 2 == 0:
raise ValueError('Odd number of elements is required')Third constraint: The values must be in the range [0 , 100]:
if (i>0 and i<=100):
# Code
else: raise ValueError('Values out of range:')2) Count method
This is the key of the exercise, looping the list checking if the current value is unique in the list:
if values.count(i) == 1:
return iThanks for reading :)
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