java: add «2416. Sum of Prefix Scores of Strings»

Signed-off-by: Matej Focko <me@mfocko.xyz>

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

@@ -0,0 +1,48 @@
+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;
+  }
+}