LeetCode/java/sum-of-prefix-scores-of-strings.java

class Solution {
  private class TrieNode {
    public TrieNode[] next = new TrieNode[26];
    public int hits = 0;
  }

  private void insert(TrieNode root, String word) {
    var node = root;
    for (var c : word.toCharArray()) {
      var idx = c - 'a';
      if (node.next[idx] == null) {
        node.next[idx] = new TrieNode();
      }

      ++node.next[idx].hits;

      node = node.next[idx];
    }
  }

  private int computeScore(TrieNode root, String word) {
    var score = 0;

    var node = root;
    for (var c : word.toCharArray()) {
      var idx = c - 'a';
      score += node.next[idx].hits;

      node = node.next[idx];
    }

    return score;
  }

  public int[] sumPrefixScores(String[] words) {
    var root = new TrieNode();
    for (var word : words) {
      insert(root, word);
    }

    var scores = new int[words.length];
    for (int i = 0; i < words.length; ++i) {
      scores[i] = computeScore(root, words[i]);
    }

    return scores;
  }
}