leetcode21. Merge Two Sorted Lists(連結串列)
阿新 • • 發佈:2019-01-14
歸併連結串列, 要注意一下連結串列的初始化問題, 尤其對於指標要謹慎處理, 很容易空指標異常
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
//判斷是否存在空連結串列
if(!l1) return l2;
if(!l2) return l1;
ListNode *l3 = NULL;
if(l1->val <= l2->val) //不必考慮頭節點資料, 使用l1&l2初始化l3
l3 = l1, l1 = l1->next;
else
l3 = l2, l2 = l2->next;
ListNode * p = l3;
while(l1 && l2){
if(l1->val <= l2->val)
p->next = l1, l1 = l1->next; //防止空鏈
else
p->next = l2, l2 = l2->next;
p = p->next;
}
p->next = (l1?l1:l2); //剩餘節點直接接在後面
return l3;
}
};