(LeetCode 面试经典 150 题) 2. 两数相加 (链表)

题目:2. 两数相加


思路:链表,时间复杂度0(n)。

C++版本:

cpp 复制代码
/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode * head=new ListNode(0);
        ListNode * p=head;
        int c=0;
        while(l1!=nullptr || l2!=nullptr){
            if(l1){
                c+=l1->val;
                l1=l1->next;
            }
            if(l2){
                c+=l2->val;
                l2=l2->next;
            }
            ListNode *tmp=new ListNode(c%10);
            p->next=tmp;
            p=tmp;
            c/=10;
        }
        while(c>0){
            ListNode *tmp=new ListNode(c%10);
            p->next=tmp;
            p=tmp;
            c/=10;
        }
        if(head->next==nullptr) return head;
        return head->next;
    }
};

JAVA版本:

java 复制代码
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode head=new ListNode(0);
        ListNode p=head;
        int c=0;
        while(l1!=null || l2!=null){
            if(l1!=null){
                c+=l1.val;
                l1=l1.next;
            }
            if(l2!=null){
                c+=l2.val;
                l2=l2.next;
            }
            ListNode tmp=new ListNode(c%10);
            p.next=tmp;
            p=tmp;
            c/=10;
        }
        while(c>0){
            ListNode tmp=new ListNode(c%10);
            p.next=tmp;
            p=tmp;
            c/=10;
        }
        if(head.next==null) return head;
        return head.next;
    }
}

GO版本:

go 复制代码
/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
    head:=&ListNode{0,nil}
    p:=head
    c:=0
    for l1!=nil || l2!=nil {
        if l1!=nil {
            c+=l1.Val
            l1=l1.Next
        }
        if l2!=nil {
            c+=l2.Val
            l2=l2.Next
        }
        tmp:=&ListNode{c%10,nil}
        p.Next=tmp
        p=tmp
        c/=10
    }
    for c>0 {
        tmp:=&ListNode{c%10,nil}
        p.Next=tmp
        p=tmp
        c/=10
    }
    if head.Next==nil {
        return head
    }
    return head.Next
}