some random challenges

Author: Adrian333Dev

random/add-two-numbers.js

@@ -0,0 +1,71 @@
+class ListNode {
+	constructor(val = 0, next = null) {
+		this.val = val;
+		this.next = next;
+	}
+}
+
+/**
+ * @param {ListNode} l1
+ * @param {ListNode} l2
+ * @return {ListNode}
+ */
+const addTwoNumbers = (l1, l2) => {
+	if (!l1 && !l2) return 0;
+	if (!l1) return l2;
+	if (!l2) return l1;
+
+	let addFromPrev = l1.val + l2.val > 9,
+		head = new ListNode((l1.val + l2.val) % 10),
+		curr = head;
+	(l1 = l1.next), (l2 = l2.next);
+	while (l1 && l2) {
+		let sum = l1.val + l2.val;
+		if (addFromPrev) sum++, (addFromPrev = false);
+		if (sum > 9) (sum = sum % 10), (addFromPrev = true);
+		(l1 = l1.next), (l2 = l2.next), (curr.next = new ListNode(sum)), (curr = curr.next);
+	}
+	while (l1) {
+		let sum = l1.val;
+		if (addFromPrev) sum++, (addFromPrev = false);
+		if (sum > 9) (sum = sum % 10), (addFromPrev = true);
+		(l1 = l1.next), (curr.next = new ListNode(sum)), (curr = curr.next);
+	}
+	while (l2) {
+		let sum = l2.val;
+		if (addFromPrev) sum++, (addFromPrev = false);
+		if (sum > 9) (sum = sum % 10), (addFromPrev = true);
+		(l2 = l2.next), (curr.next = new ListNode(sum)), (curr = curr.next);
+	}
+	if (addFromPrev) curr.next = new ListNode(1);
+	return head;
+};
+
+const printList = (head) => {
+	let str = '';
+	while (head) (str += head.val + ' -> '), (head = head.next);
+	console.log(str);
+};
+
+let l1 = new ListNode(2, new ListNode(4, new ListNode(3))),
+	l2 = new ListNode(5, new ListNode(6, new ListNode(4)));
+
+printList(addTwoNumbers(l1, l2)); // 7 -> 0 -> 8
+
+l1 = new ListNode(0);
+l2 = new ListNode(0);
+
+printList(addTwoNumbers(l1, l2)); // 0
+
+l1 = new ListNode(
+	9,
+	new ListNode(
+		9,
+		new ListNode(
+			9,
+			new ListNode(9, new ListNode(9, new ListNode(9, new ListNode(9))))
+		)
+	)
+);
+l2 = new ListNode(9, new ListNode(9, new ListNode(9, new ListNode(9))));
+printList(addTwoNumbers(l1, l2)); // 8 -> 9 -> 9 -> 9 -> 0 -> 0 -> 0 -> 1

random/first-missing-positive.js

@@ -0,0 +1,20 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+const firstMissingPositive = (nums) => {
+	let min = Infinity,
+		idx = 0;
+	for (let i = 1; i < nums.length; i++) {
+		if (nums[i - 1] === nums[i]) continue;
+		const requiredInt = nums[i - 1] + 1;
+		if (nums[i] !== requiredInt) {
+			min = Math.min(min, requiredInt);
+		}
+	}
+	return min;
+};
+
+console.log(firstMissingPositive([1, 2, 0])); // 3
+console.log(firstMissingPositive([3, 4, -1, 1])); // 2
+console.log(firstMissingPositive([7, 8, 9, 11, 12])); // 1

random/reverse-integer.js

@@ -0,0 +1,15 @@
+/**
+ * @param {number} x
+ * @return {number}
+ */
+const reverse = (x) => {
+	if (x === 0) return x;
+	const negative = x < 0;
+	x = Math.abs(x);
+	let sum = 0;
+	while (x > 0) (sum += x % 10), (x = Math.floor(x / 10)), x > 0 && (sum *= 10);
+	return 2 ** 31 - 1 < sum || sum < -(2 ** 31) ? 0 : negative ? -sum : sum;
+};
+
+console.log(reverse(123));
+console.log(reverse(-123));