160.intersection-of-two-linked-lists.java

/*
 * @lc app=leetcode id=160 lang=java
 *
 * [160] Intersection of Two Linked Lists
 */

// @lc code=start
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        ListNode curA = headA;
        ListNode curB = headB;
        int lenA = 0, lenB = 0;
        while (curA != null) {
            curA = curA.next;
            lenA++;
        }
        while (curB!= null) {
            curB = curB.next;
            lenB++;
        }
        curA = headA;
        curB = headB;
        if (lenB > lenA) {
            int tmp = lenA;
            lenA = lenB;
            lenB = tmp;
            ListNode tmpNode = curA;
            curA = curB;
            curB = tmpNode;
        }
        int gap = lenA - lenB;
        while (gap-- > 0) {
            curA = curA.next;
        }
        while (curA != null) {
            if (curA == curB) {
                return curA;
            }
            curA = curA.next;
            curB = curB.next;
        }
        return null;
    }
}
// @lc code=end