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677. Map Sum Pairs 👍

  • Time:
    • Constructor: $O(1)$
    • insert(key: str, val: int): $O(|\texttt{key}|)$
    • sum(prefix: str): $O(|\texttt{prefix}|)$
  • Space: $O(|\texttt{insert()})$
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struct TrieNode {
  vector<shared_ptr<TrieNode>> children;
  int sum = 0;
  TrieNode() : children(26) {}
};

class MapSum {
 public:
  void insert(string key, int val) {
    const int diff = val - keyToVal[key];
    shared_ptr<TrieNode> node = root;
    for (const char c : key) {
      const int i = c - 'a';
      if (node->children[i] == nullptr)
        node->children[i] = make_shared<TrieNode>();
      node = node->children[i];
      node->sum += diff;
    }
    keyToVal[key] = val;
  }

  int sum(string prefix) {
    shared_ptr<TrieNode> node = root;
    for (const char c : prefix) {
      const int i = c - 'a';
      if (node->children[i] == nullptr)
        return 0;
      node = node->children[i];
    }
    return node->sum;
  }

 private:
  shared_ptr<TrieNode> root = make_shared<TrieNode>();
  unordered_map<string, int> keyToVal;
};

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class TrieNode {
  public TrieNode[] children = new TrieNode[26];
  public int sum = 0;
}

class MapSum {
  public void insert(String key, int val) {
    final int diff = val - keyToVal.getOrDefault(key, 0);
    TrieNode node = root;
    for (final char c : key.toCharArray()) {
      final int i = c - 'a';
      if (node.children[i] == null)
        node.children[i] = new TrieNode();
      node = node.children[i];
      node.sum += diff;
    }
    keyToVal.put(key, val);
  }

  public int sum(String prefix) {
    TrieNode node = root;
    for (final char c : prefix.toCharArray()) {
      final int i = c - 'a';
      if (node.children[i] == null)
        return 0;
      node = node.children[i];
    }
    return node.sum;
  }

  private TrieNode root = new TrieNode();
  private Map<String, Integer> keyToVal = new HashMap<>();
}

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class TrieNode:
  def __init__(self):
    self.children: dict[str, TrieNode] = {}
    self.sum = 0


class MapSum:
  def __init__(self):
    self.root = TrieNode()
    self.keyToVal = {}

  def insert(self, key: str, val: int) -> None:
    diff = val - self.keyToVal.get(key, 0)
    node: TrieNode = self.root
    for c in key:
      node = node.children.setdefault(c, TrieNode())
      node.sum += diff
    self.keyToVal[key] = val

  def sum(self, prefix: str) -> int:
    node: TrieNode = self.root
    for c in prefix:
      if c not in node.children:
        return 0
      node = node.children[c]
    return node.sum