DEV Community

Cover image for 1915. Number of Wonderful Substrings
MD ARIFUL HAQUE
MD ARIFUL HAQUE

Posted on • Edited on

1915. Number of Wonderful Substrings

1915. Number of Wonderful Substrings

Medium

A wonderful string is a string where at most one letter appears an odd number of times.

  • For example, "ccjjc" and "abab" are wonderful, but "ab" is not.

Given a string word that consists of the first ten lowercase English letters ('a' through 'j'), return the number of wonderful non-empty substrings in word. If the same substring appears multiple times in word, then count each occurrence separately.

A substring is a contiguous sequence of characters in a string.

Example 1:

  • Input: word = "aba"
  • Output: 4
  • Explanation: The four wonderful substrings are underlined below:
    • "aba" -> "a"
    • "aba" -> "b"
    • "aba" -> "a"
    • "aba" -> "aba"

Example 2:

  • Input: word = "aabb"
  • Output: 9
  • Explanation: The nine wonderful substrings are underlined below:
    • "aabb" -> "a"
    • "aabb" -> "aa"
    • "aabb" -> "aab"
    • "aabb" -> "aabb"
    • "aabb" -> "a"
    • "aabb" -> "abb"
    • "aabb" -> "b"
    • "aabb" -> "bb"
    • "aabb" -> "b"

Example 3:

  • Input: word = "he"
  • Output: 2
  • Explanation: The two wonderful substrings are underlined below:
    • "he" -> "h"
    • "he" -> "e"

Constraints:

  • 1 <= word.length <= 105
  • word consists of lowercase English letters from 'a' to 'j'.

Solution:

class Solution {

    /**
     * @param String $word
     * @return Integer
     */
    function wonderfulSubstrings($word) {
        $ans = 0;
        $prefix = 0;
        $count = array_fill(0, 1024, 0);
        $count[0] = 1;

        foreach(str_split($word) as $c) {
            $prefix ^= 1 << ord($c) - ord('a');
            $ans += $count[$prefix];
            for ($i = 0; $i < 10; ++$i)
                $ans += $count[$prefix ^ 1 << $i];
            ++$count[$prefix];
        }

        return $ans;
    }
}
Enter fullscreen mode Exit fullscreen mode

Contact Links

If you found this series helpful, please consider giving the repository a star on GitHub or sharing the post on your favorite social networks 😍. Your support would mean a lot to me!

Postmark Image

Speedy emails, satisfied customers

Are delayed transactional emails costing you user satisfaction? Postmark delivers your emails almost instantly, keeping your customers happy and connected.

Sign up

Top comments (0)

Sentry image

See why 4M developers consider Sentry, “not bad.”

Fixing code doesn’t have to be the worst part of your day. Learn how Sentry can help.

Learn more