Add solution #677

Author: JoshCrozier

0677-map-sum-pairs.js

@@ -0,0 +1,39 @@
+/**
+ * 677. Map Sum Pairs
+ * https://leetcode.com/problems/map-sum-pairs/
+ * Difficulty: Medium
+ *
+ * Design a map that allows you to do the following:
+ * - Maps a string key to a given value.
+ * - Returns the sum of the values that have a key with a prefix equal to a given string.
+ *
+ * Implement the MapSum class:
+ * - MapSum() Initializes the MapSum object.
+ * - void insert(String key, int val) Inserts the key-val pair into the map. If the key
+ *   already existed, the original key-value pair will be overridden to the new one.
+ * - int sum(string prefix) Returns the sum of all the pairs' value whose key starts
+ *   with the prefix.
+ */
+
+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) {
+  return [...this.map.entries()].reduce((total, [key, val]) => {
+    return key.startsWith(prefix) ? total + val : total;
+  }, 0);
+};

README.md

@@ -510,6 +510,7 @@
 674|[Longest Continuous Increasing Subsequence](./0674-longest-continuous-increasing-subsequence.js)|Easy|
 675|[Cut Off Trees for Golf Event](./0675-cut-off-trees-for-golf-event.js)|Hard|
 676|[Implement Magic Dictionary](./0676-implement-magic-dictionary.js)|Medium|
+677|[Map Sum Pairs](./0677-map-sum-pairs.js)|Medium|
 680|[Valid Palindrome II](./0680-valid-palindrome-ii.js)|Easy|
 684|[Redundant Connection](./0684-redundant-connection.js)|Medium|
 686|[Repeated String Match](./0686-repeated-string-match.js)|Easy|