長度最小的子數組

• https://leetcode.cn/problems/minimum-size-subarray-sum/

思路

• 使用滑動窗口，left表示滑動窗口的起始點，right表示滑動窗口的終點

class Solution:def minSubArrayLen(self, target: int, nums: List[int]) -> int:left = 0     # left表示滑動窗口的起始點res = float('inf')   # float('inf')表示無窮大total = 0    # 記錄滑動窗口中的和length = len(nums)for right in range(length):   # right表示滑動窗口的終點total += nums[right]while total >= target:l = right - left + 1res = min(l, res)total -= nums[left]left += 1if res == float('inf'):   # 說明在遍歷過程中，初始的res始終沒有被替換，即nums的總和小于targetreturn 0else:                # res被替換了，說明有滿足條件的return res

螺旋矩陣

• https://leetcode.cn/problems/spiral-matrix-ii/

思路

• 每遍歷一條邊時，保持循環不變量原則，即每一條邊都遵循左閉右開[)的原則

class Solution:def generateMatrix(self, n: int) -> List[List[int]]:arr = [ [None]*n for _ in range(n)]   # 先申請好一段二維數組startx, starty = 0, 0   # 每遍歷一圈的起始位置offset = 1               # 右開count = 1               # 技術器loop = n // 2           # 總共螺旋的圈數mid = n // 2             # 若n為奇數，則最中間元素的坐標while loop > 0:for y in range(starty, n - offset):    # 上邊arr[startx][y] = countcount+=1for x in range(startx, n - offset):   # 右邊arr[x][n - offset] = countcount+=1for y in range(n - offset, starty, -1):   # 下邊arr[n - offset][y] = countcount+=1for x in range(n - offset, startx, -1):   # 左邊arr[x][starty] = countcount+=1startx += 1starty += 1offset += 1loop -= 1if n%2 == 1:   # 若n為奇數arr[mid][mid] = n*nreturn arr

總結