Map Sum Pairs

Description

Implement a MapSum class with insert, and sum methods.

For the method insert, you'll be given a pair of (string, integer). The string represents the key and the integer represents the value. If the key already existed, then the original key-value pair will be overridden to the new one.

For the method sum, you'll be given a string representing the prefix, and you need to return the sum of all the pairs' value whose key starts with the prefix.

Example 1:

Input: insert("apple", 3), Output: Null
Input: sum("ap"), Output: 3
Input: insert("app", 2), Output: Null
Input: sum("ap"), Output: 5

Solution(javascript)

/*
 * @lc app=leetcode id=677 lang=javascript
 *
 * [677] Map Sum Pairs
 */

// @lc code=start
class TrieNode {
  constructor(val) {
    this.num = 0
    this.val = val
    this.children = {}
  }
}
/**
 * Initialize your data structure here.
 */
const MapSum = function () {
  this.root = new TrieNode('')
}

/**
 * @param {string} key
 * @param {number} val
 * @return {void}
 */
MapSum.prototype.insert = function (key, val) {
  let node = this.root
  for (const c of key) {
    if (!node.children[c]) {
      node.children[c] = new TrieNode(c)
    }
    node = node.children[c]
  }
  node.num = val
}

/**
 * @param {string} prefix
 * @return {number}
 */
MapSum.prototype.sum = function (prefix) {
  let sum = 0
  let node = this.root
  for (const c of prefix) {
    if (!node.children[c]) {
      return 0
    }
    node = node.children[c]
  }
  const aux = (node) => {
    sum += node.num
    const { children } = node
    Object.keys(children).forEach((key) => {
      aux(children[key])
    })
  }
  aux(node)
  return sum
}

/**
 * Your MapSum object will be instantiated and called as such:
 * var obj = new MapSum()
 * obj.insert(key,val)
 * var param_2 = obj.sum(prefix)
 */
// @lc code=end