LeetCode 2. 两数相加

迭代

java

/**
 * Definition for singly-linked list.
 **/
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode p = l1;
        ListNode q = l2;
        ListNode result = new ListNode();
        ListNode o = result;
        int carray = 0;
        while(p!=null && q!=null){
            int sum = p.val + q.val + carray;
            o.next = new ListNode(sum%10);
            carray=sum/10;
            p = p.next;
            q = q.next;
            o = o.next;
        }
        while(p!=null){
            int sum = carray + p.val;
            o.next = new ListNode(sum%10);
            carray = sum/10;
            o = o.next;
            p = p.next;
        }
        while(q!=null){
            int sum = carray + q.val;
            o.next = new ListNode(sum%10);
            carray = sum/10;
            o = o.next;
            q = q.next;
        }
        if(carray==1){
            o.next = new ListNode(1);
        }
        return result.next;
    }
}

C++

/**
 * 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* result = new ListNode();
        ListNode* res = result;
        ListNode* p = l1;
        ListNode* q = l2;
        int carray = 0;
        int sum = 0;
        while(p!=nullptr && q !=nullptr){
            sum = p->val + q->val + carray;
            carray = sum/10;
            res->next = new ListNode(sum%10);
            p = p->next;
            q = q->next;
            res = res->next;
        }
        while(p!=nullptr){
            sum = p->val + carray;
            carray = sum/10;
            res->next = new ListNode(sum%10);
            res = res->next;
            p = p->next;
        }
        while(q!=nullptr){
            sum = q->val + carray;
            carray = sum/10;
            res->next = new ListNode(sum%10);
            res = res->next;
            q = q->next;
        }
        if(carray!=0){
            res->next = new ListNode(carray);
        }
        return result->next;
    }
};

递归

Java

class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int total = l1.val + l2.val;
        int next = total/10;
        ListNode res = new ListNode(total%10);
        if(l1.next!=null || l2.next!=null || next != 0){
            if(l1.next==null){
                l1 = new ListNode(0);
            }else{
                l1 = l1.next;
            }
            if(l2.next==null){
                l2 = new ListNode(0);
            }else{
                l2 = l2.next;
            }
            l1.val += next;
            res.next = addTwoNumbers(l1,l2);
        }
        return res;
    }
}

C++

/**
 * 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) {
        int sum = l1->val + l2->val;
        int next = sum/10;
        ListNode* res = new ListNode(sum%10);
        if(l1->next!=nullptr || l2->next!=nullptr || next !=0){
            if(l1->next==nullptr){
                l1 = new ListNode(0);
            }else{
                l1 = l1->next;
            }
            if(l2->next==nullptr){
                l2 = new ListNode(0);
            }else{
                l2 = l2->next;
            }
            l1->val+=next;
            res->next = addTwoNumbers(l1,l2);
        }
 
        return res;
    }
};