Grokking Google Coding Interview
Ask Author
Back to course home

0% completed

Vote For New Content
Unique Length-3 Palindromic Subsequences (medium)
Table of Contents

Contents are not accessible

Contents are not accessible

Contents are not accessible

Contents are not accessible

Contents are not accessible

Problem Statement

Given a string s, return the total number of unique palindromes of length 3 which are subsequences of s. Even if multiple ways exist to obtain the same subsequence, it is still only counted once.

A palindrome string is a sequence of characters that reads the same backward as forward.

A subsequence is a sequence that can be derived from another sequence by deleting some or no elements without changing the order of the remaining elements.

Examples

Example 1:

  • Input: s = "abcba"
  • Expected Output: 3
  • Justification: The three unique length-3 palindromic subsequences are "aba", "aca", and "bcb".

Example 2:

  • Input: s = "aba"
  • Expected Output: 1
  • Justification: The one unique length-3 palindromic subsequence is "aba".

Example 3:

  • Input: s = "aacbbcacb"
  • Expected Output: 9
  • Justification: The nine unique length-3 palindromic subsequences are "aaa", "aca", "aba", "ccc", "cbc", "bbb", "bab", "cac", and "bcb".

Try it yourself

Try solving this question here:

Python3
Python3
. . . .

.....

.....

.....

Like the course? Get enrolled and start learning!

Table of Contents

Contents are not accessible

Contents are not accessible

Contents are not accessible

Contents are not accessible

Contents are not accessible