Leetcode—2.两数相加【中等】

2023每日刷题（十五）

Leetcode—2.两数相加

迭代法实现代码

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
    struct ListNode* lc = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* p = l1;
    struct ListNode* q = l2;
    lc->next = p;
    int c = 0;
    struct ListNode* p2 = p;
    struct ListNode* q2 = q;
    while(p&&q) {
        c = p->val + q->val + c;
        int tmp = c % 10;
        c /= 10;
        p->val = tmp;
        if(p->next == NULL) {
            p2 = p;
        }
        p = p->next; 
        q = q->next;
    }
    if(p) {
        while(p) {
            c = c + p->val;
            int tmp = c % 10;
            c /= 10;
            p->val = tmp;
            if(p->next == NULL) {
                p2 = p;
            }
            p = p->next;
        }
        if(c != 0) {
            struct ListNode* s = (struct ListNode*)malloc(sizeof(struct ListNode));
            s->val = c;
            s->next = NULL;
            p2->next = s;
            c = 0;
        }
    }
    
    if(q) {
        p2->next = q;
        while(q) {
            c = c + q->val;
            int tmp = c % 10;
            c /= 10;
            q->val = tmp;
            if(q->next == NULL) {
                q2 = q;
            }
            q = q->next;
        }
        if(c != 0) {
            struct ListNode* s = (struct ListNode*)malloc(sizeof(struct ListNode));
            s->val = c;
            s->next = NULL;
            q2->next = s;
            c = 0;
        }
    }

    if(c != 0) {
        struct ListNode* s = (struct ListNode*)malloc(sizeof(struct ListNode));
        s->val = c;
        s->next = NULL;
        p2->next = s;
        c = 0;
    }
    return lc->next;
}

运行结果

递归实现代码

/**
 * 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, int carry = 0) {
        if(l1 == nullptr && l2 == nullptr) {
            return (carry? new ListNode(carry) : nullptr);
        }
        if(l1 == nullptr) {
            struct ListNode* p = l1;
            l1 = l2;
            l2 = p;
        }
        carry += l1->val + (l2? l2->val: 0);
        l1->val = carry % 10;
        l1->next = addTwoNumbers(l1->next, (l2? l2->next: nullptr), carry/10);
        return l1;
    }
};

运行结果

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