[LeetCode]Add Two Numbers

最新推荐文章于 2024-08-12 10:14:14 发布

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本文介绍如何使用C++编程语言实现两个链表表示的整数相加，通过逐位相加并处理进位来生成结果链表。

struct ListNode {
	int val;
	ListNode *next;
	ListNode(int x) : val(x), next(NULL) {}
};

class Solution {
//dummy node in the head of the result, avoid judging NULL of head
public:
	ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
		// Start typing your C/C++ solution below
		// DO NOT write int main() function
		ListNode dummy(-1);//dummy node in the head of the result, avoid judging NULL of head
		ListNode* pre = &dummy;

		ListNode* p1 = l1;
		ListNode* p2 = l2;
		int carry = 0;
		while(p1 != NULL || p2 != NULL)
		{
			int a1 = p1 == NULL ? 0 : p1->val;
			int a2 = p2 == NULL ? 0 : p2->val;
			int sum = a1+a2+carry;
			carry = sum/10;
			ListNode* node = new ListNode(sum%10);
			pre->next = node;
			pre = pre->next;
			p1 = p1 == NULL ? NULL : p1->next;
			p2 = p2 == NULL ? NULL : p2->next;
		}
		if(carry != 0) pre->next = new ListNode(carry);
		return dummy.next;
	}
};

second time

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
        ListNode dummy(0);
        ListNode* prev = &dummy;
        int carry = 0;
        while(l1 != NULL || l2 != NULL || carry != 0)
        {
            int a = 0;
            int b = 0;
            
            if(l1 != NULL) a = l1->val, l1 = l1->next;
            if(l2 != NULL) b = l2->val, l2 = l2->next;
            int sum = a+b+carry;
            prev->next = new ListNode(sum%10);
            prev = prev->next;
            carry = sum/10;
        }
        
        return dummy.next;
    }
};