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Problem · String

Palindromic Strings

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Problem statement

A string is a palindrome if the reverse of the string is the same as the original string. An analyst at HackerRank is tasked to analyze an array of n strings that consist of lowercase English characters.

In one operation, the analyst chooses 4 integers, namely x, y, i, j such that 1 ≤ x, y ≤ n, 1 ≤ i ≤ length(arr[x]), 1 ≤ j ≤ length(arr[y]) and then swaps arr[x][i] and arr[y][j] using 1-based indexing.

The analyst wishes to determine the maximum number of palindromic strings that can be obtained by performing the operation any number of times, possibly 0.

Function

countPalindromes(arr: String[]) → int

Complete the function countPalindromes in the editor below.

countPalindromes has the following parameter:

  • string arr[n]: the strings to consider

Returns

int: the maximum number of palindromic strings possible

Examples

Example 1

arr = ["pass", "sas", "asps", "df"]return = 3
An optimal solution produces 3 palindromes.
  • Select x = 1, y = 3, i = 3, j = 1, swap arr[1][3], arr[3][1]. Then, arr = ["paas", "sas", "ssps", "df"]
  • Select x = 1, y = 3, i = 4, j = 3, swap arr[1][4], arr[3][3]. arr = ["paap", "sas", "ssss", "df"]
    • Return 3, the number of palindromic strings.

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    public int countPalindromes(String[] arr) {
  // write your code here
}
    arr["pass", "sas", "asps", "df"]
    expected3
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