intersectionofTwoLinkedLists.js

////////////////////////////////////////////////Intersection of Two Linked Lists/////////////////////////////////////////////
// Given the heads of two singly linked-lists headA and headB, return the node at which the two lists intersect. If the two linked lists have no intersection at all, return null.
// For example, the following two linked lists begin to intersect at node c1:
// The test cases are generated such that there are no cycles anywhere in the entire linked structure.
// Note that the linked lists must retain their original structure after the function returns.
// Custom Judge:
// The inputs to the judge are given as follows (your program is not given these inputs):
// intersectVal - The value of the node where the intersection occurs. This is 0 if there is no intersected node.
// listA - The first linked list.
// listB - The second linked list.
// skipA - The number of nodes to skip ahead in listA (starting from the head) to get to the intersected node.
// skipB - The number of nodes to skip ahead in listB (starting from the head) to get to the intersected node.
// The judge will then create the linked structure based on these inputs and pass the two heads, headA and headB to your program.
// If you correctly return the intersected node, then your solution will be accepted.
// Example 1:
// Input: intersectVal = 8, listA = [4,1,8,4,5], listB = [5,6,1,8,4,5], skipA = 2, skipB = 3
// Output: Intersected at '8'
// Explanation: The intersected node's value is 8 (note that this must not be 0 if the two lists intersect).
// From the head of A, it reads as [4,1,8,4,5]. From the head of B, it reads as [5,6,1,8,4,5]. There are 2 nodes before the
// intersected node in A; There are 3 nodes before the intersected node in B.
// Example 2:
// Input: intersectVal = 2, listA = [1,9,1,2,4], listB = [3,2,4], skipA = 3, skipB = 1
// Output: Intersected at '2'
// Explanation: The intersected node's value is 2 (note that this must not be 0 if the two lists intersect).
// From the head of A, it reads as [1,9,1,2,4]. From the head of B, it reads as [3,2,4]. There are 3 nodes before the
// intersected node in A; There are 1 node before the intersected node in B.
// Example 3:
// Input: intersectVal = 0, listA = [2,6,4], listB = [1,5], skipA = 3, skipB = 2
// Output: No intersection
// Explanation: From the head of A, it reads as [2,6,4]. From the head of B, it reads as [1,5]. Since the two lists do not
// intersect, intersectVal must be 0, while skipA and skipB can be arbitrary values.
// Explanation: The two lists do not intersect, so return null.
/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

/**
 * @param {ListNode} headA
 * @param {ListNode} headB
 * @return {ListNode}
 */
 const getIntersectionNode = function(headA, headB) {
    let a = headA, b = headB
    while (a !== b) {
        a = !a ? headB : a.next
        b = !b ? headA : b.next
    }
    return a
};

// console.log(getIntersectionNode([4,1,8,4,5], [5,6,1,8,4,5]));
// console.log(getIntersectionNode([1,9,1,2,4], [3,2,4]));
// console.log(getIntersectionNode([2,6,4], [1,5]));