Leetcode - Minimum Size Subarray Sum Solution

Given an array of positive integers nums and a positive integer target, return the minimal length of a contiguous subarray [numsl, numsl+1, ..., numsr-1, numsr] of which the sum is greater than or equal to target. If there is no such subarray, return 0 instead.

Example 1:

Input: target = 7, nums = [2,3,1,2,4,3]
Output: 2
Explanation: The subarray [4,3] has the minimal length under the problem constraint.

Example 2:

Input: target = 4, nums = [1,4,4]
Output: 1

Example 3:

Input: target = 11, nums = [1,1,1,1,1,1,1,1]
Output: 0

Constraints:

• 1 <= target <= 109
• 1 <= nums.length <= 105
• 1 <= nums[i] <= 105

Follow up: If you have figured out the O(n) solution, try coding another solution of which the time complexity is O(n log(n)).

Solution in python

class Solution:
    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
        l = 0
        r = 0
        s = 0
        m = float('inf')
        while r<len(nums):
            while s<target and r<len(nums):
                s += nums[r]
                r +=1
            while s>=target and l<len(nums):
                if s >= target:
                    m = min(m,r-l)
                s -= nums[l]
                l += 1

        if m == float('inf'):
            return 0
        return m