From 1aab307ed7a0e9c539bc450fdf7fbdc3082a1b67 Mon Sep 17 00:00:00 2001 From: Eyjan_Huang <81480748+Eyjan-Huang@users.noreply.github.com> Date: Sat, 14 Aug 2021 23:18:15 +0800 Subject: [PATCH 01/15] =?UTF-8?q?=E6=9B=B4=E6=96=B0=20=E9=9D=A2=E8=AF=95?= =?UTF-8?q?=E9=A2=9802.07=20=E9=93=BE=E8=A1=A8=E7=9B=B8=E4=BA=A4python?= =?UTF-8?q?=E4=BB=A3=E7=A0=81?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 用更简单的逻辑完成这道题。 --- problems/面试题02.07.链表相交.md | 37 ++++++++----------------- 1 file changed, 12 insertions(+), 25 deletions(-) diff --git a/problems/面试题02.07.链表相交.md b/problems/面试题02.07.链表相交.md index 9acda71c..8c3a5831 100644 --- a/problems/面试题02.07.链表相交.md +++ b/problems/面试题02.07.链表相交.md @@ -160,34 +160,21 @@ Python： class Solution: def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> ListNode: - lengthA,lengthB = 0,0 - curA,curB = headA,headB - while(curA!=None): #求链表A的长度 - curA = curA.next - lengthA +=1 - - while(curB!=None): #求链表B的长度 - curB = curB.next - lengthB +=1 - - curA, curB = headA, headB + """ + 根据快慢法则，走的快的一定会追上走得慢的。 + 在这道题里，有的链表短，他走完了就去走另一条链表，我们可以理解为走的快的指针。 - if lengthB>lengthA: #让curA为最长链表的头，lenA为其长度 - lengthA, lengthB = lengthB, lengthA - curA, curB = curB, curA + 那么，只要其中一个链表走完了，就去走另一条链表的路。如果有交点，他们最终一定会在同一个 + 位置相遇 + """ + cur_a, cur_b = headA, headB # 用两个指针代替a和b - gap = lengthA - lengthB #求长度差 - while(gap!=0): - curA = curA.next #让curA和curB在同一起点上 - gap -= 1 - while(curA!=None): - if curA == curB: - return curA - else: - curA = curA.next - curB = curB.next - return None + while cur_a != cur_b: + cur_a = cur_a.next if cur_a else headB # 如果a走完了，那么就切换到b走 + cur_b = cur_b.next if cur_b else headA # 同理，b走完了就切换到a + + return cur_a ``` Go： From b2122ef9e2306aa6e097446897195e7114dd09d0 Mon Sep 17 00:00:00 2001 From: reoooh Date: Sun, 15 Aug 2021 00:42:42 +0800 Subject: [PATCH 02/15] =?UTF-8?q?=E6=B7=BB=E5=8A=A00977=E6=9C=89=E5=BA=8F?= =?UTF-8?q?=E6=95=B0=E7=BB=84=E7=9A=84=E5=B9=B3=E6=96=B9=20Ruby=20?= =?UTF-8?q?=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0977.有序数组的平方.md | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/problems/0977.有序数组的平方.md b/problems/0977.有序数组的平方.md index 9e71ec0d..71c46401 100644 --- a/problems/0977.有序数组的平方.md +++ b/problems/0977.有序数组的平方.md @@ -252,6 +252,24 @@ func sortedSquares(_ nums: [Int]) -> [Int] { } ``` +Ruby: + +```ruby +def sorted_squares(nums) + left, right, result = 0, nums.size - 1, [] + while left <= right + if nums[left]**2 > nums[right]**2 + result << nums[left]**2 + left += 1 + else + result << nums[right]**2 + right -= 1 + end + end + result.reverse +end +``` + ----------------------- From 12e1cd35441cdc6ca30a190eebd6cbe945a06f66 Mon Sep 17 00:00:00 2001 From: Steve0x2a Date: Sun, 15 Aug 2021 13:33:14 +0800 Subject: [PATCH 03/15] =?UTF-8?q?=E6=B7=BB=E5=8A=A00724=E5=AF=BB=E6=89=BE?= =?UTF-8?q?=E6=95=B0=E7=BB=84=E7=9A=84=E4=B8=AD=E5=BF=83=E7=B4=A2=E5=BC=95?= =?UTF-8?q?=20Python=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0724.寻找数组的中心索引.md | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/problems/0724.寻找数组的中心索引.md b/problems/0724.寻找数组的中心索引.md index 3ed68d47..052d4c02 100644 --- a/problems/0724.寻找数组的中心索引.md +++ b/problems/0724.寻找数组的中心索引.md @@ -90,6 +90,15 @@ class Solution { ## Python ```python +class Solution: + def pivotIndex(self, nums: List[int]) -> int: + numSum = sum(nums) #数组总和 + leftSum = 0 + for i in range(len(nums)): + if numSum - leftSum -nums[i] == leftSum: #左右和相等 + return i + leftSum += nums[i] + return -1 ``` ## Go From 082e3ae66e2c36508aadfc4fea58a32fbf8b803f Mon Sep 17 00:00:00 2001 From: Steve0x2a Date: Sun, 15 Aug 2021 13:58:49 +0800 Subject: [PATCH 04/15] =?UTF-8?q?=E6=B7=BB=E5=8A=A00922=E6=8C=89=E5=A5=87?= =?UTF-8?q?=E5=81=B6=E6=8E=92=E5=BA=8F=E6=95=B0=E7=BB=84II=20Python?= =?UTF-8?q?=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0922.按奇偶排序数组II.md | 27 +++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/problems/0922.按奇偶排序数组II.md b/problems/0922.按奇偶排序数组II.md index 92db204d..97d7091e 100644 --- a/problems/0922.按奇偶排序数组II.md +++ b/problems/0922.按奇偶排序数组II.md @@ -149,7 +149,32 @@ class Solution { ## Python -```python +```python3 +#方法2 +class Solution: + def sortArrayByParityII(self, nums: List[int]) -> List[int]: + result = [0]*len(nums) + evenIndex = 0 + oddIndex = 1 + for i in range(len(nums)): + if nums[i] % 2: #奇数 + result[oddIndex] = nums[i] + oddIndex += 2 + else: #偶数 + result[evenIndex] = nums[i] + evenIndex += 2 + return result + +#方法3 +class Solution: + def sortArrayByParityII(self, nums: List[int]) -> List[int]: + oddIndex = 1 + for i in range(0,len(nums),2): #步长为2 + if nums[i] % 2: #偶数位遇到奇数 + while nums[oddIndex] % 2: #奇数位找偶数 + oddIndex += 2 + nums[i], nums[oddIndex] = nums[oddIndex], nums[i] + return nums ``` ## Go From a108aadfb58516205cdc2d5b53406efea784e910 Mon Sep 17 00:00:00 2001 From: Steve0x2a Date: Sun, 15 Aug 2021 14:15:43 +0800 Subject: [PATCH 05/15] =?UTF-8?q?=E6=B7=BB=E5=8A=A00234=E5=9B=9E=E6=96=87?= =?UTF-8?q?=E9=93=BE=E8=A1=A8=20Python=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0234.回文链表.md | 57 ++++++++++++++++++++++++++++++++++- 1 file changed, 56 insertions(+), 1 deletion(-) diff --git a/problems/0234.回文链表.md b/problems/0234.回文链表.md index 6a24b1d0..b3ad899c 100644 --- a/problems/0234.回文链表.md +++ b/problems/0234.回文链表.md @@ -148,7 +148,62 @@ public: ## Python -```python +```python3 +#数组模拟 +class Solution: + def isPalindrome(self, head: ListNode) -> bool: + length = 0 + tmp = head + while tmp: #求链表长度 + length += 1 + tmp = tmp.next + + result = [0] * length + tmp = head + index = 0 + while tmp: #链表元素加入数组 + result[index] = tmp.val + index += 1 + tmp = tmp.next + + i, j = 0, length - 1 + while i < j: # 判断回文 + if result[i] != result[j]: + return False + i += 1 + j -= 1 + return True + +#反转后半部分链表 +class Solution: + def isPalindrome(self, head: ListNode) -> bool: + if head == None or head.next == None: + return True + slow, fast = head, head + while fast and fast.next: + pre = slow + slow = slow.next + fast = fast.next.next + + pre.next = None # 分割链表 + cur1 = head # 前半部分 + cur2 = self.reverseList(slow) # 反转后半部分，总链表长度如果是奇数，cur2比cur1多一个节点 + while cur1: + if cur1.val != cur2.val: + return False + cur1 = cur1.next + cur2 = cur2.next + return True + + def reverseList(self, head: ListNode) -> ListNode: + cur = head + pre = None + while(cur!=None): + temp = cur.next # 保存一下cur的下一个节点 + cur.next = pre # 反转 + pre = cur + cur = temp + return pre ``` ## Go From 2f39c7df81006b963f48cf79251e1f83ff8a61bb Mon Sep 17 00:00:00 2001 From: Steve0x2a Date: Sun, 15 Aug 2021 14:40:48 +0800 Subject: [PATCH 06/15] =?UTF-8?q?=E6=B7=BB=E5=8A=A00143=E9=87=8D=E6=8E=92?= =?UTF-8?q?=E9=93=BE=E8=A1=A8=20Python=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0143.重排链表.md | 54 +++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/problems/0143.重排链表.md b/problems/0143.重排链表.md index 62232051..76df63b7 100644 --- a/problems/0143.重排链表.md +++ b/problems/0143.重排链表.md @@ -222,7 +222,61 @@ public class ReorderList { ``` Python： +```python3 +# 方法二 双向队列 +class Solution: + def reorderList(self, head: ListNode) -> None: + """ + Do not return anything, modify head in-place instead. + """ + d = collections.deque() + tmp = head + while tmp.next: # 链表除了首元素全部加入双向队列 + d.append(tmp.next) + tmp = tmp.next + tmp = head + while len(d): # 一后一前加入链表 + tmp.next = d.pop() + tmp = tmp.next + if len(d): + tmp.next = d.popleft() + tmp = tmp.next + tmp.next = None # 尾部置空 + +# 方法三 反转链表 +class Solution: + def reorderList(self, head: ListNode) -> None: + if head == None or head.next == None: + return True + slow, fast = head, head + while fast and fast.next: + slow = slow.next + fast = fast.next.next + right = slow.next # 分割右半边 + slow.next = None # 切断 + right = self.reverseList(right) #反转右半边 + left = head + # 左半边一定比右半边长, 因此判断右半边即可 + while right: + curLeft = left.next + left.next = right + left = curLeft + curRight = right.next + right.next = left + right = curRight + + + def reverseList(self, head: ListNode) -> ListNode: + cur = head + pre = None + while(cur!=None): + temp = cur.next # 保存一下cur的下一个节点 + cur.next = pre # 反转 + pre = cur + cur = temp + return pre +``` Go： JavaScript： From e35c7cc63f56f66ea37c02244481cfb45ce640b8 Mon Sep 17 00:00:00 2001 From: Steve0x2a Date: Sun, 15 Aug 2021 14:52:09 +0800 Subject: [PATCH 07/15] =?UTF-8?q?=E6=B7=BB=E5=8A=A00724=E5=AF=BB=E6=89=BE?= =?UTF-8?q?=E6=95=B0=E7=BB=84=E7=9A=84=E4=B8=AD=E5=BF=83=E7=B4=A2=E5=BC=95?= =?UTF-8?q?=20Python=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0724.寻找数组的中心索引.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/problems/0724.寻找数组的中心索引.md b/problems/0724.寻找数组的中心索引.md index 052d4c02..b4115893 100644 --- a/problems/0724.寻找数组的中心索引.md +++ b/problems/0724.寻找数组的中心索引.md @@ -89,7 +89,7 @@ class Solution { ## Python -```python +```python3 class Solution: def pivotIndex(self, nums: List[int]) -> int: numSum = sum(nums) #数组总和 From 5850f6d636af38f3edbac46ef4e8e81a8271b8f9 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E4=BD=99=E6=9D=9C=E6=9E=97?= Date: Sun, 15 Aug 2021 15:34:34 +0800 Subject: [PATCH 08/15] =?UTF-8?q?=E6=B7=BB=E5=8A=A00059.=E8=9E=BA=E6=97=8B?= =?UTF-8?q?=E7=9F=A9=E9=98=B5II=20Swift=20=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0059.螺旋矩阵II.md | 55 +++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) diff --git a/problems/0059.螺旋矩阵II.md b/problems/0059.螺旋矩阵II.md index e46dae6d..6df8c83d 100644 --- a/problems/0059.螺旋矩阵II.md +++ b/problems/0059.螺旋矩阵II.md @@ -302,6 +302,61 @@ func generateMatrix(n int) [][]int { } ``` +Swift: + +```swift +func generateMatrix(_ n: Int) -> [[Int]] { + var result = [[Int]](repeating: [Int](repeating: 0, count: n), count: n) + + var startRow = 0 + var startColumn = 0 + var loopCount = n / 2 + let mid = n / 2 + var count = 1 + var offset = 1 + var row: Int + var column: Int + + while loopCount > 0 { + row = startRow + column = startColumn + + for c in column ..< startColumn + n - offset { + result[startRow][c] = count + count += 1 + column += 1 + } + + for r in row ..< startRow + n - offset { + result[r][column] = count + count += 1 + row += 1 + } + + for _ in startColumn ..< column { + result[row][column] = count + count += 1 + column -= 1 + } + + for _ in startRow ..< row { + result[row][column] = count + count += 1 + row -= 1 + } + + startRow += 1 + startColumn += 1 + offset += 2 + loopCount -= 1 + } + + if (n % 2) != 0 { + result[mid][mid] = count + } + return result +} +``` From 71ee2d5d0bc9dba8f2d83156c05ea17a5353036a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E4=BD=99=E6=9D=9C=E6=9E=97?= Date: Sun, 15 Aug 2021 21:35:27 +0800 Subject: [PATCH 09/15] =?UTF-8?q?=E6=B7=BB=E5=8A=A00203.=E7=A7=BB=E9=99=A4?= =?UTF-8?q?=E9=93=BE=E8=A1=A8=E5=85=83=E7=B4=A0=20Swift=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0203.移除链表元素.md | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/problems/0203.移除链表元素.md b/problems/0203.移除链表元素.md index a2c6e90d..9235d47e 100644 --- a/problems/0203.移除链表元素.md +++ b/problems/0203.移除链表元素.md @@ -304,6 +304,34 @@ var removeElements = function(head, val) { }; ``` +Swift: + +```swift +/** + * Definition for singly-linked list. + * public class ListNode { + * public var val: Int + * public var next: ListNode? + * public init() { self.val = 0; self.next = nil; } + * public init(_ val: Int) { self.val = val; self.next = nil; } + * public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; } + * } + */ +func removeElements(_ head: ListNode?, _ val: Int) -> ListNode? { + let dummyNode = ListNode() + dummyNode.next = head + var currentNode = dummyNode + while let curNext = currentNode.next { + if curNext.val == val { + currentNode.next = curNext.next + } else { + currentNode = curNext + } + } + return dummyNode.next +} +``` + From d350a4dd8206f8cae4773d96e0a985e954276fe6 Mon Sep 17 00:00:00 2001 From: Eyjan_Huang <81480748+Eyjan-Huang@users.noreply.github.com> Date: Mon, 16 Aug 2021 15:42:28 +0800 Subject: [PATCH 10/15] =?UTF-8?q?=E6=9B=B4=E6=96=B0=200349.=E4=B8=A4?= =?UTF-8?q?=E4=B8=AA=E6=95=B0=E7=BB=84=E7=9A=84=E4=BA=A4=E9=9B=86.md=20pyt?= =?UTF-8?q?hon=E4=BB=A3=E7=A0=81=E7=AE=80=E5=8C=96?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 一行代码解决 --- problems/0349.两个数组的交集.md | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff --git a/problems/0349.两个数组的交集.md b/problems/0349.两个数组的交集.md index 29c1c144..2dd52a85 100644 --- a/problems/0349.两个数组的交集.md +++ b/problems/0349.两个数组的交集.md @@ -121,13 +121,7 @@ Python： ```python class Solution: def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]: - result_set = set() - - set1 = set(nums1) - for num in nums2: - if num in set1: - result_set.add(num) # set1里出现的nums2元素 存放到结果 - return list(result_set) + return list(set(nums1) & set(nums2)) # 两个数组线变成集合，求交集后还原为数组 ``` From 46c1084f69621055c9fc862cd61042194a6db4c0 Mon Sep 17 00:00:00 2001 From: Eyjan_Huang <81480748+Eyjan-Huang@users.noreply.github.com> Date: Mon, 16 Aug 2021 15:43:09 +0800 Subject: [PATCH 11/15] =?UTF-8?q?=E6=9B=B4=E6=96=B0=200349.=E4=B8=A4?= =?UTF-8?q?=E4=B8=AA=E6=95=B0=E7=BB=84=E7=9A=84=E4=BA=A4=E9=9B=86.md=20?= =?UTF-8?q?=E9=94=99=E5=88=AB=E5=AD=97=E4=BF=AE=E6=AD=A3?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0349.两个数组的交集.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/problems/0349.两个数组的交集.md b/problems/0349.两个数组的交集.md index 2dd52a85..7489352d 100644 --- a/problems/0349.两个数组的交集.md +++ b/problems/0349.两个数组的交集.md @@ -121,7 +121,7 @@ Python： ```python class Solution: def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]: - return list(set(nums1) & set(nums2)) # 两个数组线变成集合，求交集后还原为数组 + return list(set(nums1) & set(nums2)) # 两个数组先变成集合，求交集后还原为数组 ``` From fbeb80f14ad127e1d47c549c1c2063715896a6bf Mon Sep 17 00:00:00 2001 From: Eyjan_Huang <81480748+Eyjan-Huang@users.noreply.github.com> Date: Mon, 16 Aug 2021 18:24:43 +0800 Subject: [PATCH 12/15] =?UTF-8?q?=E6=9B=B4=E6=96=B0=200202.=E5=BF=AB?= =?UTF-8?q?=E4=B9=90=E6=95=B0.md=20python=E4=BB=A3=E7=A0=81=E7=AE=80?= =?UTF-8?q?=E5=8C=96?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 利用闭包的特性，修改了原本python代码中不符合PEP3的写法，以及赘余的代码。思路保持一致 --- problems/0202.快乐数.md | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) diff --git a/problems/0202.快乐数.md b/problems/0202.快乐数.md index 1c630b6a..2e784e6a 100644 --- a/problems/0202.快乐数.md +++ b/problems/0202.快乐数.md @@ -111,25 +111,29 @@ Python： ```python class Solution: def isHappy(self, n: int) -> bool: - set_ = set() - while 1: - sum_ = self.getSum(n) - if sum_ == 1: + def calculate_happy(num): + sum_ = 0 + + # 从个位开始依次取，平方求和 + while num: + sum_ += (num % 10) ** 2 + num = num // 10 + return sum_ + + # 记录中间结果 + record = set() + + while True: + n = calculate_happy(n) + if n == 1: return True - #如果这个sum曾经出现过，说明已经陷入了无限循环了，立刻return false - if sum_ in set_: + + # 如果中间结果重复出现，说明陷入死循环了，该数不是快乐数 + if n in record: return False else: - set_.add(sum_) - n = sum_ - - #取数值各个位上的单数之和 - def getSum(self, n): - sum_ = 0 - while n > 0: - sum_ += (n%10) * (n%10) - n //= 10 - return sum_ + record.add(n) + ``` Go： From 175f1c5e1a459e72511ae56ce33828a8fc367690 Mon Sep 17 00:00:00 2001 From: Eyjan_Huang <81480748+Eyjan-Huang@users.noreply.github.com> Date: Mon, 16 Aug 2021 19:11:16 +0800 Subject: [PATCH 13/15] =?UTF-8?q?=E7=AE=80=E5=8C=96=200001.=E4=B8=A4?= =?UTF-8?q?=E6=95=B0=E4=B9=8B=E5=92=8C.md=20python=E4=BB=A3=E7=A0=81?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 原代码过于赘余，需要遍历两次且可读性较差。更新后的代码在维持题主题意的基础上的一次优化 --- problems/0001.两数之和.md | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/problems/0001.两数之和.md b/problems/0001.两数之和.md index f8c9da5f..9b961d0b 100644 --- a/problems/0001.两数之和.md +++ b/problems/0001.两数之和.md @@ -110,13 +110,14 @@ Python： ```python class Solution: def twoSum(self, nums: List[int], target: int) -> List[int]: - hashmap={} - for ind,num in enumerate(nums): - hashmap[num] = ind - for i,num in enumerate(nums): - j = hashmap.get(target - num) - if j is not None and i!=j: - return [i,j] + records = dict() + + # 用枚举更方便，就不需要通过索引再去取当前位置的值 + for idx, val in enumerate(nums): + if target - val not in records: + records[val] = idx + else: + return [records[target - val], idx] # 如果存在就返回字典记录索引和当前索引 ``` From a648b12e31822b023501bb60e12403b6ba54095d Mon Sep 17 00:00:00 2001 From: Steve0x2a Date: Tue, 17 Aug 2021 13:59:39 +0800 Subject: [PATCH 14/15] =?UTF-8?q?=E6=B7=BB=E5=8A=A00129=E6=B1=82=E6=A0=B9?= =?UTF-8?q?=E5=88=B0=E5=8F=B6=E5=AD=90=E8=8A=82=E7=82=B9=E6=95=B0=E5=AD=97?= =?UTF-8?q?=E4=B9=8B=E5=92=8C=20Python3=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../0129.求根到叶子节点数字之和.md | 25 +++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/problems/0129.求根到叶子节点数字之和.md b/problems/0129.求根到叶子节点数字之和.md index b37270e2..17642793 100644 --- a/problems/0129.求根到叶子节点数字之和.md +++ b/problems/0129.求根到叶子节点数字之和.md @@ -165,7 +165,32 @@ public: Java： Python： +```python3 +class Solution: + def sumNumbers(self, root: TreeNode) -> int: + res = 0 + path = [] + def backtrace(root): + nonlocal res + if not root: return # 节点空则返回 + path.append(root.val) + if not root.left and not root.right: # 遇到了叶子节点 + res += get_sum(path) + if root.left: # 左子树不空 + backtrace(root.left) + if root.right: # 右子树不空 + backtrace(root.right) + path.pop() + def get_sum(arr): + s = 0 + for i in range(len(arr)): + s = s * 10 + arr[i] + return s + + backtrace(root) + return res +``` Go： JavaScript： From 91ef55c83dd07556e08f6c7ab5c644ccf73c3e27 Mon Sep 17 00:00:00 2001 From: XuDaHaoRen <1547794387@qq.com> Date: Tue, 17 Aug 2021 16:40:56 +0800 Subject: [PATCH 15/15] =?UTF-8?q?problems/0001.=E4=B8=A4=E6=95=B0=E4=B9=8B?= =?UTF-8?q?=E5=92=8C=E8=B6=85=E9=93=BE=E6=8E=A5=E6=9B=BF=E6=8D=A2=E6=88=90?= =?UTF-8?q?=E4=B8=AA=E4=BA=BA=E7=BD=91=E7=AB=99?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0001.两数之和.md | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/problems/0001.两数之和.md b/problems/0001.两数之和.md index f8c9da5f..a4f63afd 100644 --- a/problems/0001.两数之和.md +++ b/problems/0001.两数之和.md @@ -9,7 +9,7 @@ ## 1. 两数之和 -https://leetcode-cn.com/problems/two-sum/ +[力扣题目链接](https://leetcode-cn.com/problems/two-sum/) 给定一个整数数组 nums 和一个目标值 target，请你在该数组中找出和为目标值的那 两个 整数，并返回他们的数组下标。 @@ -29,10 +29,10 @@ https://leetcode-cn.com/problems/two-sum/ 很明显暴力的解法是两层for循环查找，时间复杂度是O(n^2)。 建议大家做这道题目之前，先做一下这两道 -* [242. 有效的字母异位词](https://mp.weixin.qq.com/s/ffS8jaVFNUWyfn_8T31IdA) -* [349. 两个数组的交集](https://mp.weixin.qq.com/s/aMSA5zrp3jJcLjuSB0Es2Q) +* [242. 有效的字母异位词](https://www.programmercarl.com/0242.有效的字母异位词.html) +* [349. 两个数组的交集](https://www.programmercarl.com/0349.两个数组的交集.html) -[242. 有效的字母异位词](https://mp.weixin.qq.com/s/ffS8jaVFNUWyfn_8T31IdA) 这道题目是用数组作为哈希表来解决哈希问题，[349. 两个数组的交集](https://mp.weixin.qq.com/s/aMSA5zrp3jJcLjuSB0Es2Q)这道题目是通过set作为哈希表来解决哈希问题。 +[242. 有效的字母异位词](https://www.programmercarl.com/0242.有效的字母异位词.html) 这道题目是用数组作为哈希表来解决哈希问题，[349. 两个数组的交集](https://www.programmercarl.com/0349.两个数组的交集.html)这道题目是通过set作为哈希表来解决哈希问题。 本题呢，则要使用map，那么来看一下使用数组和set来做哈希法的局限。 @@ -51,7 +51,7 @@ C++中map，有三种类型： std::unordered_map 底层实现为哈希表，std::map 和std::multimap 的底层实现是红黑树。 -同理，std::map 和std::multimap 的key也是有序的（这个问题也经常作为面试题，考察对语言容器底层的理解）。 更多哈希表的理论知识请看[关于哈希表，你该了解这些！](https://mp.weixin.qq.com/s/RSUANESA_tkhKhYe3ZR8Jg)。 +同理，std::map 和std::multimap 的key也是有序的（这个问题也经常作为面试题，考察对语言容器底层的理解）。 更多哈希表的理论知识请看[关于哈希表，你该了解这些！](https://www.programmercarl.com/哈希表理论基础.html)。 **这道题目中并不需要key有序，选择std::unordered_map 效率更高！**