【剑指offer第12天】双指针（简单）

快来打我* 2022-09-12 04:49 129阅读 0赞

![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAJ-alkw_size_20_color_FFFFFF_t_70_g_se_x_16]

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */
    class Solution { 
        public ListNode mergeTwoLists(ListNode l1, ListNode l2) { 
            if(l1 == null){ 
                return l2;
            }else if(l2 == null){ 
                return l1;
            }
            ListNode head = l1;
            if(l1.val > l2.val){ 
                head = l2;
                l2 = l2.next;
            }else{ 
                l1 = l1.next;
            }
            ListNode cur = head;
            while(l1!=null&&l2!=null){ 
                if(l1.val <= l2.val){ 
                    cur.next = l1;
                    l1 = l1.next;
                }else{ 
                    cur.next = l2;
                    l2 = l2.next;
                }
                cur = cur.next;
            }
            if(l1 != null){ 
                cur.next = l1;
            }else if(l2 != null){ 
                cur.next = l2;
            }
            return head;
        }
    }

设置dum结点，dum.next指向头结点

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */
    class Solution { 
        public ListNode mergeTwoLists(ListNode l1, ListNode l2) { 
            ListNode dum = new ListNode(0),cur = dum;
            while(l1!=null&&l2!=null){ 
                if(l1.val<=l2.val){ 
                    cur.next = l1;
                    l1 = l1.next;
                }else{ 
                    cur.next = l2;
                    l2 = l2.next;
                }
                cur = cur.next;
            }
            cur.next = l1!=null?l1:l2;
            return dum.next;
        }
    }

![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAJ-alkw_size_20_color_FFFFFF_t_70_g_se_x_16 1]

/** * 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) { 
            if(headA == null||headB == null){ return null;}
            ListNode l1 = headA,l2 = headB;
            while(l1 != l2){ 
                if(l1 == null){ l1 = headB;}
                else{ l1 = l1.next;}
                if(l2 == null){ l2 = headA;}
                else{ l2 = l2.next;}
            }
            return l1;
        }
    }

[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAJ-alkw_size_20_color_FFFFFF_t_70_g_se_x_16]: /images/20220828/b55ec0cc1c4a495999143c0337c0205f.png
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAJ-alkw_size_20_color_FFFFFF_t_70_g_se_x_16 1]: /images/20220828/de8d6324a7a5475e98b39557cf27cd87.png