From 891d82652e8a662bc74bf16167c865ae24001e67 Mon Sep 17 00:00:00 2001 From: missannas <42210208+missannas@users.noreply.github.com> Date: Sat, 8 Dec 2018 15:26:11 +0800 Subject: [PATCH 1/6] Create readme.md --- miss-ann/add-two-number/readme.md | 138 ++++++++++++++++++++++++++++++ 1 file changed, 138 insertions(+) create mode 100644 miss-ann/add-two-number/readme.md diff --git a/miss-ann/add-two-number/readme.md b/miss-ann/add-two-number/readme.md new file mode 100644 index 0000000..2874b28 --- /dev/null +++ b/miss-ann/add-two-number/readme.md @@ -0,0 +1,138 @@ +# 两数相加 + +今天是小安开始Leetcode刷题的第二题，正文开始ing😎 + +## 题目描述 +给出两个 **非空** 的链表用来表示两个非负的整数。其中，它们各自的位数是按照 **逆序** 的方式存储的，并且它们的每个节点只能存储 **一位** 数字。 +如果，我们将这两个数相加起来，则会返回一个新的链表来表示它们的和。 +您可以假设除了数字 0 之外，这两个数都不会以 0 开头。[题目原址](https://leetcode-cn.com/problems/add-two-numbers/) +**示例** +> 输入：(2 -> 4 -> 3) + (5 -> 6 -> 4) +> 输出：7 -> 0 -> 8 +> 原因：342 + 465 = 807 + +## 方法：初等数学 + +### 思想 +我们使用变量来跟踪进位，并从包含最低有效位的表头开始模拟逐位相加的过程。 +![两数相加的可视化：342+258=708](https://img-blog.csdnimg.cn/20181207210901837.png) +如两数相加的可视化图所示，我们首先从最低有效位也就是列表 l1 和 l2 的表头开始相加。由于每位数字都应当处于 0...9 的范围内，我们计算两个数字的和时可能会出现“溢出”。例如，$5 + 7 = 12$ 。在这种情况下，我们会将当前位的数值设置为 sum%10，并将进位 $count =sum/10$ 带入下一次迭代。 +**请特别注意以下情况：** + +|测试用例 |说明 | +|--|--| +| l1=[0,1],l2=[0,1,2] |当一个列表比另一个列表长时。 | +| l1=[],l2=[0,1]| 当一个列表为空时，即出现空列表。| +|l1=[9,9],l2=[1]|求和运算最后可能出现额外的进位，这一点很容易被遗忘 | +### 代码实现 +【C实现】 + +``` +/** + * Definition for singly-linked list. + * struct ListNode { + * int val; + * struct ListNode *next; + * }; + */ +struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) { + struct ListNode *head=(struct ListNode *)malloc(sizeof(struct ListNode));//head用于返回新链表 + struct ListNode *tail=head; + int sum,count=0; //sum用来存储当前位相加，若有进位则count=sum/10 + while(l1!= NULL ||l2!=NULL){ + int x = (l1!=NULL)?l1->val:0; + int y = (l2!=NULL)?l2->val:0; + int sum =count+x+y; + count=sum/10; + tail->next=(struct ListNode *)malloc(sizeof(struct ListNode)); + tail =tail->next; + tail->val=sum%10;//相加后存储值为除去进位10 + if(l1!=NULL) l1=l1->next; + if(l2!=NULL) l2=l2->next; + } + if(count>0){//判断最后一位是否需要进位 + tail->next=(struct ListNode *)malloc(sizeof(struct ListNode)); + tail=tail->next; + tail->val=count; + } + tail->next=NULL; + tail=head; + head=head->next; + free(tail); + return head;//返回头结点的下一节点 + } +``` +【Java实现】 + +``` +/** + * Definition for singly-linked list. + * public class ListNode { + * int val; + * ListNode next; + * ListNode(int x) { val = x; } + * } + */ +class Solution { + public ListNode addTwoNumbers(ListNode l1, ListNode l2) { + ListNode head = new ListNode(0); + ListNode tail = head; + int count = 0; + while (l1 != null || l2 != null) { + int x = (l1 != null) ? l1.val : 0; + int y = (l2 != null) ? l2.val : 0; + int sum = count + x + y; + count = sum / 10; + tail.next = new ListNode(sum % 10); + tail = tail.next; + if (l1 != null) l1 = l1.next; + if (l2 != null) l2 = l2.next; + } + if (count > 0) { + tail.next = new ListNode(count); + } + return head.next; + + } +} +``` +【python实现】 + +``` +# Definition for singly-linked list. +# class ListNode: +# def __init__(self, x): +# self.val = x +# self.next = None + +class Solution: + def addTwoNumbers(self, l1, l2): + """ + :type l1: ListNode + :type l2: ListNode + :rtype: ListNode + """ + head = ListNode(0) + tail = head + count=0 + while(l1 or l2): + x=l1.val if l1 else 0 + y=l2.val if l2 else 0 + s=count+x+y + count=s//10 + tail.next=ListNode(s%10) + tail=tail.next + if(l1!=None): l1=l1.next + if(l2!=None): l2=l2.next + if(count>0): + tail.next=ListNode(1) + return head.next + +``` +### 复杂度分析 + - 时间复杂度：$O(max(m,n))$，假设 m 和 n分别表示 l1和 l2的长度，上面的算法最多重复 max(m, n)次。 + - 空间复杂度： $O(max(m,n))$， 新列表的长度最多为max(m,n)+1。 + + +# Thanks +一起加油哦~~ From 5b4e24dc88ce25456938aa378fdded08e9e996cf Mon Sep 17 00:00:00 2001 From: missannas <42210208+missannas@users.noreply.github.com> Date: Sat, 8 Dec 2018 15:27:01 +0800 Subject: [PATCH 2/6] Create al.c --- miss-ann/add-two-number/al.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 miss-ann/add-two-number/al.c diff --git a/miss-ann/add-two-number/al.c b/miss-ann/add-two-number/al.c new file mode 100644 index 0000000..9d576bf --- /dev/null +++ b/miss-ann/add-two-number/al.c @@ -0,0 +1,33 @@ +/** + * Definition for singly-linked list. + * struct ListNode { + * int val; + * struct ListNode *next; + * }; + */ +struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) { + struct ListNode *head=(struct ListNode *)malloc(sizeof(struct ListNode));//head用于返回新链表 + struct ListNode *tail=head; + int sum,count=0; //sum用来存储当前位相加，若有进位则count=sum/10 + while(l1!= NULL ||l2!=NULL){ + int x = (l1!=NULL)?l1->val:0; + int y = (l2!=NULL)?l2->val:0; + int sum =count+x+y; + count=sum/10; + tail->next=(struct ListNode *)malloc(sizeof(struct ListNode)); + tail =tail->next; + tail->val=sum%10;//相加后存储值为除去进位10 + if(l1!=NULL) l1=l1->next; + if(l2!=NULL) l2=l2->next; + } + if(count>0){//判断最后一位是否需要进位 + tail->next=(struct ListNode *)malloc(sizeof(struct ListNode)); + tail=tail->next; + tail->val=count; + } + tail->next=NULL; + tail=head; + head=head->next; + free(tail); + return head;//返回头结点的下一节点 + } From 3349f8a37dadcbd1f3ab641d56afb4456fec2dc8 Mon Sep 17 00:00:00 2001 From: missannas <42210208+missannas@users.noreply.github.com> Date: Sat, 8 Dec 2018 15:28:30 +0800 Subject: [PATCH 3/6] Create al.c --- miss-ann/add-two-number/al/al.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 miss-ann/add-two-number/al/al.c diff --git a/miss-ann/add-two-number/al/al.c b/miss-ann/add-two-number/al/al.c new file mode 100644 index 0000000..9d576bf --- /dev/null +++ b/miss-ann/add-two-number/al/al.c @@ -0,0 +1,33 @@ +/** + * Definition for singly-linked list. + * struct ListNode { + * int val; + * struct ListNode *next; + * }; + */ +struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) { + struct ListNode *head=(struct ListNode *)malloc(sizeof(struct ListNode));//head用于返回新链表 + struct ListNode *tail=head; + int sum,count=0; //sum用来存储当前位相加，若有进位则count=sum/10 + while(l1!= NULL ||l2!=NULL){ + int x = (l1!=NULL)?l1->val:0; + int y = (l2!=NULL)?l2->val:0; + int sum =count+x+y; + count=sum/10; + tail->next=(struct ListNode *)malloc(sizeof(struct ListNode)); + tail =tail->next; + tail->val=sum%10;//相加后存储值为除去进位10 + if(l1!=NULL) l1=l1->next; + if(l2!=NULL) l2=l2->next; + } + if(count>0){//判断最后一位是否需要进位 + tail->next=(struct ListNode *)malloc(sizeof(struct ListNode)); + tail=tail->next; + tail->val=count; + } + tail->next=NULL; + tail=head; + head=head->next; + free(tail); + return head;//返回头结点的下一节点 + } From eb3543edfa91a1c0b18a2a5b0043ba78bdd821a6 Mon Sep 17 00:00:00 2001 From: missannas <42210208+missannas@users.noreply.github.com> Date: Sat, 8 Dec 2018 15:28:58 +0800 Subject: [PATCH 4/6] Create al.java --- miss-ann/add-two-number/al/al.java | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) create mode 100644 miss-ann/add-two-number/al/al.java diff --git a/miss-ann/add-two-number/al/al.java b/miss-ann/add-two-number/al/al.java new file mode 100644 index 0000000..b205fc8 --- /dev/null +++ b/miss-ann/add-two-number/al/al.java @@ -0,0 +1,29 @@ +/** + * Definition for singly-linked list. + * public class ListNode { + * int val; + * ListNode next; + * ListNode(int x) { val = x; } + * } + */ +class Solution { + public ListNode addTwoNumbers(ListNode l1, ListNode l2) { + ListNode dummyHead = new ListNode(0); + ListNode p = l1, q = l2, curr = dummyHead; + int carry = 0; + while (p != null || q != null) { + int x = (p != null) ? p.val : 0; + int y = (q != null) ? q.val : 0; + int sum = carry + x + y; + carry = sum / 10; + curr.next = new ListNode(sum % 10); + curr = curr.next; + if (p != null) p = p.next; + if (q != null) q = q.next; + } + if (carry > 0) { + curr.next = new ListNode(carry); + } + return dummyHead.next; + } +} From 4ebb942e2b9fb3a8e535c3f0386eb1fc32bcc2cc Mon Sep 17 00:00:00 2001 From: missannas <42210208+missannas@users.noreply.github.com> Date: Sat, 8 Dec 2018 15:29:31 +0800 Subject: [PATCH 5/6] Create al.py --- miss-ann/add-two-number/al/al.py | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) create mode 100644 miss-ann/add-two-number/al/al.py diff --git a/miss-ann/add-two-number/al/al.py b/miss-ann/add-two-number/al/al.py new file mode 100644 index 0000000..4814b75 --- /dev/null +++ b/miss-ann/add-two-number/al/al.py @@ -0,0 +1,28 @@ +# Definition for singly-linked list. +# class ListNode: +# def __init__(self, x): +# self.val = x +# self.next = None + +class Solution: + def addTwoNumbers(self, l1, l2): + """ + :type l1: ListNode + :type l2: ListNode + :rtype: ListNode + """ + head = ListNode(0) + tail = head + count=0 + while(l1 or l2): + x=l1.val if l1 else 0 + y=l2.val if l2 else 0 + s=count+x+y + count=s//10 + tail.next=ListNode(s%10) + tail=tail.next + if(l1!=None): l1=l1.next + if(l2!=None): l2=l2.next + if(count>0): + tail.next=ListNode(1) + return head.next From f8ec484d89dbb99d4dc1c9422d121930de55ad19 Mon Sep 17 00:00:00 2001 From: missannas <42210208+missannas@users.noreply.github.com> Date: Sat, 8 Dec 2018 15:29:49 +0800 Subject: [PATCH 6/6] Delete al.c --- miss-ann/add-two-number/al.c | 33 --------------------------------- 1 file changed, 33 deletions(-) delete mode 100644 miss-ann/add-two-number/al.c diff --git a/miss-ann/add-two-number/al.c b/miss-ann/add-two-number/al.c deleted file mode 100644 index 9d576bf..0000000 --- a/miss-ann/add-two-number/al.c +++ /dev/null @@ -1,33 +0,0 @@ -/** - * Definition for singly-linked list. - * struct ListNode { - * int val; - * struct ListNode *next; - * }; - */ -struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) { - struct ListNode *head=(struct ListNode *)malloc(sizeof(struct ListNode));//head用于返回新链表 - struct ListNode *tail=head; - int sum,count=0; //sum用来存储当前位相加，若有进位则count=sum/10 - while(l1!= NULL ||l2!=NULL){ - int x = (l1!=NULL)?l1->val:0; - int y = (l2!=NULL)?l2->val:0; - int sum =count+x+y; - count=sum/10; - tail->next=(struct ListNode *)malloc(sizeof(struct ListNode)); - tail =tail->next; - tail->val=sum%10;//相加后存储值为除去进位10 - if(l1!=NULL) l1=l1->next; - if(l2!=NULL) l2=l2->next; - } - if(count>0){//判断最后一位是否需要进位 - tail->next=(struct ListNode *)malloc(sizeof(struct ListNode)); - tail=tail->next; - tail->val=count; - } - tail->next=NULL; - tail=head; - head=head->next; - free(tail); - return head;//返回头结点的下一节点 - }