Add solution #1622

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,427 LeetCode solutions in JavaScript
+# 1,428 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1251,6 +1251,7 @@
 1619|[Mean of Array After Removing Some Elements](./solutions/1619-mean-of-array-after-removing-some-elements.js)|Easy|
 1620|[Coordinate With Maximum Network Quality](./solutions/1620-coordinate-with-maximum-network-quality.js)|Medium|
 1621|[Number of Sets of K Non-Overlapping Line Segments](./solutions/1621-number-of-sets-of-k-non-overlapping-line-segments.js)|Medium|
+1622|[Fancy Sequence](./solutions/1622-fancy-sequence.js)|Hard|
 1657|[Determine if Two Strings Are Close](./solutions/1657-determine-if-two-strings-are-close.js)|Medium|
 1668|[Maximum Repeating Substring](./solutions/1668-maximum-repeating-substring.js)|Easy|
 1669|[Merge In Between Linked Lists](./solutions/1669-merge-in-between-linked-lists.js)|Medium|

solutions/1622-fancy-sequence.js

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+/**
+ * 1622. Fancy Sequence
+ * https://leetcode.com/problems/fancy-sequence/
+ * Difficulty: Hard
+ *
+ * Write an API that generates fancy sequences using the append, addAll, and multAll operations.
+ *
+ * Implement the Fancy class:
+ * - Fancy() Initializes the object with an empty sequence.
+ * - void append(val) Appends an integer val to the end of the sequence.
+ * - void addAll(inc) Increments all existing values in the sequence by an integer inc.
+ * - void multAll(m) Multiplies all existing values in the sequence by an integer m.
+ * - int getIndex(idx) Gets the current value at index idx (0-indexed) of the sequence modulo
+ *   109 + 7. If the index is greater or equal than the length of the sequence, return -1.
+ */
+
+var Fancy = function() {
+  this.sequence = [];
+  this.additive = 0n;
+  this.multiplicative = 1n;
+  this.MOD = 1000000007n;
+};
+
+/**
+ * @param {number} val
+ * @return {void}
+ */
+Fancy.prototype.append = function(val) {
+  const valBig = BigInt(val);
+  const inverse = this.modInverse(this.multiplicative);
+  const adjustedVal = ((valBig - this.additive + this.MOD) * inverse) % this.MOD;
+  this.sequence.push(adjustedVal);
+};
+
+/**
+ * @param {number} inc
+ * @return {void}
+ */
+Fancy.prototype.addAll = function(inc) {
+  this.additive = (this.additive + BigInt(inc)) % this.MOD;
+};
+
+/**
+ * @param {number} m
+ * @return {void}
+ */
+Fancy.prototype.multAll = function(m) {
+  const mBig = BigInt(m);
+  this.additive = (this.additive * mBig) % this.MOD;
+  this.multiplicative = (this.multiplicative * mBig) % this.MOD;
+};
+
+/**
+ * @param {number} idx
+ * @return {number}
+ */
+Fancy.prototype.getIndex = function(idx) {
+  if (idx >= this.sequence.length) return -1;
+  return Number((this.sequence[idx] * this.multiplicative + this.additive) % this.MOD);
+};
+
+/**
+ * @param {number} a
+ * @return {number}
+ */
+Fancy.prototype.modInverse = function(a) {
+  let m = this.MOD;
+  const m0 = m;
+  let x = 1n;
+  let y = 0n;
+
+  a = a % m;
+  while (a > 1n) {
+    const q = a / m;
+    [a, m] = [m, a % m];
+    [x, y] = [y, x - q * y];
+  }
+
+  return x < 0n ? x + m0 : x;
+};