MapSumPairs.js

// Source : https://leetcode.com/problems/map-sum-pairs
// Author : Dean Shi
// Date   : 2017-09-21

/***************************************************************************************
 *
 * 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
 *
 ***************************************************************************************/

/**
 * Initialize your data structure here.
 */
var MapSum = function() {
    this.map = new Map()
};

/**
 * @param {string} key
 * @param {number} val
 * @return {void}
 */
MapSum.prototype.insert = function(key, val) {
    this.map.set(key, val)
};

/**
 * @param {string} prefix
 * @return {number}
 */
MapSum.prototype.sum = function(prefix) {
    let sum = 0
    for (let [key, val] of this.map) {
        if (key.startsWith(prefix)) sum += val
    }
    return sum
};

/**
 * Your MapSum object will be instantiated and called as such:
 * var obj = Object.create(MapSum).createNew()
 * obj.insert(key,val)
 * var param_2 = obj.sum(prefix)
 */