小黑代码

class Solution:
    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
        # 数组长度
        n = len(nums)
        # 定义双指针
        head = 0
        tail = 0
        # 中间变量
        sum_ = 0
        # 结果变量
        min_ = n + 1
        # 开始迭代 
        while head < n:
            # 尾部指针右移
            while tail < n and sum_ < target:
                sum_ += nums[tail]
                tail += 1
            # 记录长度
            if sum_ >= target and min_ > tail - head:
                min_ = tail - head
            sum_ -= nums[head]
            head += 1
        return min_ if min_ != n + 1 else 0

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小黑根据思路自己尝试前缀和二分法

class Solution:
    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
        # 数组长度
        n = len(nums)
        # 计算前缀和
        arr = [0] + [nums[0]] * n
        for i in range(1, n+1):
            arr[i] = arr[i-1] + nums[i-1]
        # 结果变量
        res = n + 1
        # 开始进行二分查找
        print(arr)
        for i in range(n+1):
            if arr[i] < target:
                continue
            l = self.left_search(arr[:i], arr[i] - target)
            length = i - l + 1 if arr[i] - target < arr[l] else i - l
            if length < res:
                res = length
        return res if res != n + 1 else 0
       
    def left_search(self, arr, target):
        # 初始化双指针
        left = 0
        right = len(arr) - 1
        while left <= right:
            mid = (left + right) // 2
            if arr[mid] < target:
                left = mid + 1
            else:
                right = mid - 1
        return left

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前缀和二分法

class Solution:
    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
        # 数组长度
        n = len(nums)
        # 构造前缀和数组
        arr = [0]
        for i in range(n):
            arr.append(nums[i]+arr[i])
        # 开始进行二分查找大于等于arr[i]+target的最近左位置
        # 结果变量
        res = n + 1
        for i in range(n):
            end = self.left_search(arr,i+1, target+arr[i])
            if end == n + 1:
                continue
            length = end - i
            if length < res:
                res = length
        return res if res != n + 1 else 0
    
    def left_search(self, arr, start, target):
        n = len(arr)
        # 定义左右指针
        start = start
        end = n - 1
        while start <= end:
            mid = (start + end) // 2
            if arr[mid] < target:
                start = mid + 1
            else:
                end = mid - 1
        return start

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双指针法

class Solution:
    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
        # 数组长度
        n = len(nums)
        # 中间变量
        sum_ = 0
        # 头尾指针
        head = 0
        tail = 0
        # 结果变量
        res = n + 1
        # 开始双指针迭代
        while tail < n:
            sum_ += nums[tail]
            tail += 1
            while sum_ >= target:
                if tail - head < res:
                    res = tail - head
                sum_ -= nums[head]
                head += 1
        return res if res != n + 1 else 0