链表算法之【合并两个有序链表】

目录

LeetCode-21题

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LeetCode-21题

将两个升序链表合并成一个新的升序链表并返回

class Solution {
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        if (list1 == null)
            return list2;
        if (list2 == null)
            return list1;

        ListNode dummyHead = new ListNode();
        ListNode curr = dummyHead;
        // 双指针
        ListNode p1 = list1;
        ListNode p2 = list2;

        while (p1 != null && p2 != null) {
            // 链入节点值较小的节点
            if (p1.val < p2.val) {
                curr.next = p1;
                p1 = p1.next;
            } else {
                curr.next = p2;
                p2 = p2.next;
            }
            curr = curr.next;
        }
        
        // 处理剩余节点
        if (p1 != null)
            curr.next = p1;
        if (p2 != null)
            curr.next = p2;

        return dummyHead.next;
    }

    private static class ListNode {
        int val;
        ListNode next;

        ListNode() {
        }

        ListNode(int val) {
            this.val = val;
        }

        ListNode(int val, ListNode next) {
            this.val = val;
            this.next = next;
        }
    }
}