-
【每日一题】实现一个完全二叉树-Python-20211110 at 2021年11月11日
参考代码:
class TreeNode: def __init__(self, val): self.val = val self.left = None self.right = None class Solution: def isComplete(self, root): if root is None: return True queue = [root] index = 0 while index < len(queue): if queue[index] is not None: queue.append(queue[index].left) queue.append(queue[index].right) index += 1 while queue[-1] is None: queue.pop() for q in queue: if q is None: return False return True -
【每日一题】整数反转-Python-20211109 at 2021年11月11日
参考代码:
class Solution: def reverseInteger(self, n): if n == 0: return 0 neg = 1 if n < 0: neg, n = -1, -n revers = 0 while n > 0: reverse = reverse * 10 + n % 10 n = n // 10 reverse = reverse * neg if reverse < - (1 << 31) or reverse > (1 << 31) - 1: return 0 return reverse -
【每日一题】合并两个排序链表-Python-20211108 at 2021年11月09日
参考代码:
class ListNode: def __init__(self, val): self.val = val self.next = None class Solution: def mergeTwoLists(self, l1, l2): dummy = ListNode(0) tmp = dummy while l1 != None and l2 != None: if l1.val < l2.val: tmp.next = l1 else: tmp.next = l2 l2 = l2.next tmp = tmp.next if l1 != None: tmp.next = l1 else: tmp.next = l2 return dummy.next -
【每日一题】克隆二叉树-Python-20211107 at 2021年11月08日
参考代码:
class TreeNode: def __init__(self, val): self.val = val self.left, self.right = None, None class Solution: def cloneTree(self, root): if root is None: return None clone_root = TreeNode(root.val) clone_root.left = self.cloneTree(root.left) clone_root.right = self.cloneTree(root.right) -
【每日一题】删除元素-Python-20211106 at 2021年11月07日
参考代码：
class Solution: def removeElement(self, A, elem): j = len(A) - 1 for i in range(len(A) - 1, -1, -1): if A[i] == elem: A[i], A[j] = A[j], A[i] j -= 1 return j + 1 -
【每日一题】链表倒数第 n 个节点-Python-20211105 at 2021年11月06日
参考代码:
class ListNode(object): def __int__(self, val): self.val = val self.next = None class Solution: def nthToLast(self, head, n): if head is None or n < 1: return None cur = head.next while cur is not None: cur.pre = head cur = cur.next head = head.next n -= 1 while n > 0: head = head.pre n -= 1 return head -
【每日一题】找出最长单词-Python-20211104 at 2021年11月05日
参考代码:
class Solution: def longesWords(self, dictionary): answer = [] maxLength = 0 for item in dictionary: if len(item) > maxLength: maxLength = len(item) answer = [item] elif len(item) == maxLength: answer.append(item) return answer -
【每日一题】两个字符串是变位词-Python-20211103 at 2021年11月05日
参考代码:
class Solution: def anagram(self, s, t): set_s = [0] * 256 set_t = [0] * 256 for i in range(0, len(s)): set_s[ord(s[i])] += 1 for i in range(0, len(t)): set_t[ord(t[i])] += 1 for i in range(0, 256): if set_s[i] != set_t[i]: return False return True -
【每日一题】两个字符串是变位词-Python-20211103 at 2021年11月04日
参考代码：
class Solution: def anagram(self, s, t): set_s = [0] * 256 set_t = [0] * 256 for i in range(0, len(s)): set_s[ord(s[i])] += 1 for i in range(0, len(t)): set_t[ord(t[i])] += 1 for i in range(0, 256): if set_s[i] != set_t[i]: return False return True -
【每日一题】判断尾数-Python-20211102 at 2021年11月03日
参考代码:
class Solution: def judeTheLastNumber(self, str): if str[-1] == -1: return 2 for i in range(-2, -len(str) - 1, -1): if str[i] == 0: return -1 * ((i * -1 + 1) % 2) + 2 return -1 * (len(str) % 2) + 2 -
【每日一题】计算二叉树某层节点之和-Python-20211101 at 2021年11月02日
参考代码:
class TreeNode: def __init__(self, val): self.val = val self.left, self.right = None, None class Solution: def levelSum(self, root, level): p = [] self.dfs(root, p, 1, level) return sum(p) def dfs(self, root, p, dep, level): if root is None: return if dep == level: p.append(root.val) return self.dfs(root.left, p, dep + 1, level) self.dfs(root.right, p, dep + 1, level) -
【每日一题】找出数组中第二大的数-Python-20211030 at 2021年11月01日
参考代码:
class TreeNode: def __init__(self, val): self.val = val self.left, self.right = None, None class Solution: def leafSum(self, root): p = [] self.dfs(root, p) return sum(p) def dfs(self, root, p): if root is None: return if root.left is None and root.right is None: p.append(root.val) self.dfs(root.left, p) self.dfs(root.right, p) -
【每日一题】找出数组中第二大的数-Python-20211030 at 2021年10月31日
参考代码:
class Solution: def secondMax(self, nums): maxValue = max(nums[0], nums[1]) secValue = min(nums[0], nums[1]) for i in range(2, len(nums)): if nums[i] > maxValue: secValue = maxValue maxValue = nums[i] elif nums[i] > secValue: secValue = nums[i] return secValue -
【每日一题】实现一个简易计算器-Python-20211029 at 2021年10月30日
参考代码：
class Solution: def calculate(self, a, operator, b): if operator == '+': return a + b elif operator == '-': return a - b elif operator == '*': return a * b elif operator == '/': return a/b -
【每日一题】单词出现频率统计-Python-20211028 at 2021年10月29日
参考代码:
class Solution: def topKFrequentWords(self, words, k): dict = {} res = [] for word in words: if word not in dict: dict[word] = 1 else: dict[word] += 1 sorted_d = sorted(dict.items(), key = lambda x:x[1], reverse=True) for i in range(k): res.append(sorted_d[i][0]) return res -
【每日一题】计算链表节点数-Python-20211027 at 2021年10月29日
参考代码:
class ListNode(object): def __init__(self, val, next = None) -> None: self.val = val self.next = next class Solution: def countNodes(self, head): cnt = 0 while head is not None: cnt += 1 head = head.next return cnt -
【每日一题】字符大小写转换-Python-20211026 at 2021年10月27日
参考代码:
class Solution: def lowercaseToUpper(self, character): return chr(ord(character) - 32) -
【每日一题】最小路径和-Python-20211025 at 2021年10月26日
参考代码:
class Solution: def minPathSum(self, grid): for i in range(len(grid)): for j in range(len(grid[0])): if i == 0 and j > 0: grid[i][j] += grid[i][j - 1] elif j == 0 and i > 0: grid[i][j] += min(grid[i-1][j], grid[i][j-1]) elif i > 0 and j > 0: grid[i][j] += min(grid[i-1][j], grid[i][j-1]) return grid[len(grid) - 1][len(grid[0]) - 1] -
【每日一题】合并排序数组-Python-20211024 at 2021年10月25日
参考代码:
class Solution: def mergeSortedArray(self, A, m, B, n): i, j = m - 1, n - 1 t = len(A) - 1 while i >= 0 or j >= 0: if i < 0 or (j >= 0 and B[j] > A[i]): A[t] = B[j] j -= 1 else: A[t] = A[i] i -= 1 t -= 1 -
【每日一题】查找数组中没有出现的所有数字-Python-20211023 at 2021年10月24日
参考代码：
class Solution: def findNumbers(self, nums): n = len(nums) s = set(nums) res = [i for i in range(1, n + 1) if i not in s] return res -
【每日一题】七进制-Python-20211022 at 2021年10月23日
参考代码:
class Solution: def convertToBase7(self, num): if num < 0: return '-' + self.convertToBase7(-num) if num < 7: return str(num) return self.convertToBase7(num//7) + str(num % 7) -
【每日一题】首字母大写-Python-20211021 at 2021年10月22日
参考代码:
class Solution: def capitalizesFirst(self, s): n = len(s) s1 = list(s) if s1[0] >= 'a' and s1[0] <= 'z': s1[0] = chr(ord(s1[0]) - 32) for i in range(1, n): if s1[i -1] == '' and s1[i] != '': s1[i] = chr(ord(s1[i]) - 32) return ''.join(s1) -
【每日一题】二叉树最长连续序列 -Python-20211020 at 2021年10月21日
参考代码:
class TreeNode: def __init__(self, val): self.val = val self.left = None self.right = None class Solution: def longestConsecutive(self, root): return self.helper(root, None, 0) def helper(self, root, parent, len): if root is None: return len if parent != None and root.val == parent.val + 1: len += 1 else: len = 1 return max(len, max(self.helper(root.left, root, len), self.helper(root.right, root, len))) -
【每日一题】玩具工厂 -Python-20211019 at 2021年10月20日
参考代码:
class Toy: def talk(self): raise NotImplementedError("This method should have implemented") class Dog(Toy): def talk(self): print("Wow") class Cat(Toy): def talk(self): print("Meow") class ToyFactory: def getToy(self, type): if type == "Dog": return Dog() elif type == "Cat": return Cat() return None -
【每日一题】两个排序数组合的第 k 个小元素 -Python-20211018 at 2021年10月19日
参考代码:
class Solution: def kthSmallestSum(self, A, B, k): if not A or not B: return None n, m = len(A), len(B) minheap = [A[0] + B[0], 0, 0] visited = set([0]) num = None for _ in range(k): num, x, y = heapq.heappop(minheap) if x+1 < n and (x + 1) * m + y not in visited: heapq.heappush(minheap, (A[x + 1] + B[y], x + 1, y)) visited.add((x + 1) * m + y) if y+1 < m and x * m + y + 1 not in visited: heapq.heappush(minheap, (A[x] + B[y + 1], x, y+1)) visited.add(x * m + y + 1) return num