Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Program to find length of longest substring with even vowel counts in Python
Suppose we have a string s (lowercase), we have to find the length of the longest substring where each vowel occurs even number of times.
So, if the input is like s = "anewcoffeepot", then the output will be 10, as the substring "wcoffeepot" has two vowels "o" and "e", both of which occurs two times.
To solve this, we will follow these steps −
vowels := a map assigning vowels and numeric values as {a:0, e:1, i:2, o:3, u:4}
prefix := an empty map and insert a key-value pair (0, −1) into it
mask := 0, n := size of s, res := 0
for i in range 0 to n, do
if s[i] is a vowels, then
mask := mask XOR (2^vowels[s[i]])
if mask is not in prefix, then
prefix[mask] := i
otherwise,
res := maximum of res and (i − prefix[mask])
return res
Let us see the following implementation to get better understanding −
Example
class Solution:
def solve(self, s):
vowels = {"a": 0, "e": 1, "i": 2, "o": 3, "u": 4}
prefix = {0: −1}
mask = 0
n = len(s)
res = 0
for i in range(n):
if s[i] in vowels:
mask ^= 1 << vowels[s[i]]
if mask not in prefix:
prefix[mask] = i
else:
res = max(res, i − prefix[mask])
return res
ob = Solution()
s = "anewcoffeepot"
print(ob.solve(s))Input
"anewcoffeepot"
Output
10
305 Views
