力扣第160题-相交链表

题目
链接

题解

哈希表

import java.util.Set;
import java.util.HashSet;
/**
 * 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) {
        Set<ListNode> set = new HashSet<>();
        ListNode h1 = headA, h2 = headB;
        while (h1 != null) {
            set.add(h1);
            h1 = h1.next;
        }
        while (h2 != null) {
            if (set.contains(h2)) {
                return h2;
            }
            h2 = h2.next;
        }
        return null;
    }
}

双指针

import java.util.Set;
import java.util.HashSet;
/**
 * 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 h1 = headA, h2 = headB;
        while (h1 != h2) {
            h1 = h1 != null ? h1.next : headA;
            h2 = h2 != null ? h2.next : headB;
        }
        return h1;
    }
}