Add solution #1146

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,152 LeetCode solutions in JavaScript
+# 1,153 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -900,6 +900,7 @@
 1143|[Longest Common Subsequence](./solutions/1143-longest-common-subsequence.js)|Medium|
 1144|[Decrease Elements To Make Array Zigzag](./solutions/1144-decrease-elements-to-make-array-zigzag.js)|Medium|
 1145|[Binary Tree Coloring Game](./solutions/1145-binary-tree-coloring-game.js)|Medium|
+1146|[Snapshot Array](./solutions/1146-snapshot-array.js)|Medium|
 1161|[Maximum Level Sum of a Binary Tree](./solutions/1161-maximum-level-sum-of-a-binary-tree.js)|Medium|
 1189|[Maximum Number of Balloons](./solutions/1189-maximum-number-of-balloons.js)|Easy|
 1200|[Minimum Absolute Difference](./solutions/1200-minimum-absolute-difference.js)|Easy|

solutions/1146-snapshot-array.js

@@ -0,0 +1,56 @@
+/**
+ * 1146. Snapshot Array
+ * https://leetcode.com/problems/snapshot-array/
+ * Difficulty: Medium
+ *
+ * Implement a SnapshotArray that supports the following interface:
+ * - SnapshotArray(int length) initializes an array-like data structure with the given length.
+ *   Initially, each element equals 0.
+ * - void set(index, val) sets the element at the given index to be equal to val.
+ * - int snap() takes a snapshot of the array and returns the snapId: the total number of times
+ *   we called snap() minus 1.
+ * - int get(index, snapId) returns the value at the given index, at the time we took the
+ *   snapshot with the given snapId
+ */
+
+/**
+ * @param {number} length
+ */
+var SnapshotArray = function(length) {
+  this.history = new Map();
+  this.snapshots = 0;
+  this.length = length;
+};
+
+/**
+ * @param {number} index
+ * @param {number} val
+ * @return {void}
+ */
+SnapshotArray.prototype.set = function(index, val) {
+  const current = this.history.get(this.snapshots) || new Map();
+  current.set(index, val);
+  this.history.set(this.snapshots, current);
+};
+
+/**
+ * @return {number}
+ */
+SnapshotArray.prototype.snap = function() {
+  return this.snapshots++;
+};
+
+/**
+ * @param {number} index
+ * @param {number} snapId
+ * @return {number}
+ */
+SnapshotArray.prototype.get = function(index, snapId) {
+  for (let id = snapId; id >= 0; id--) {
+    const snapshot = this.history.get(id);
+    if (snapshot && snapshot.has(index)) {
+      return snapshot.get(index);
+    }
+  }
+  return 0;
+};