Leetcode 209. Minimum Size Subarray Sum

[medium]

Minimum Size Subarray Sum - LeetCode

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

[Java- Gary]

1. using two pointer to track current substring
2. keep adding nums[j] until total larger than target
3. compare the current shortest and current window
4. subtract nums[i] and move the pointer i forward
5. return the current shortest result, if result is still Integer.MAX_VALUE, return 0

[Java — O(n lg(n))]