209. Minimum Size Subarray Sum

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209. Minimum Size Subarray Sum

Description

Given an array of positive integers nums and a positive integer target, return the minimal length of a subarray whose sum is greater than or equal to target. If there is no such subarray, return 0 instead.

Example 1:

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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:

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

Example 3:

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

Constraints:

  • 1 <= target <= 10^9
  • 1 <= nums.length <= 10^5
  • 1 <= nums[i] <= 10^4

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)).

Hints/Notes

Solution

Language: C++

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class Solution {
public:
    int minSubArrayLen(int target, vector<int>& nums) {
        int left = 0, n = nums.size(), curSum = 0, res = INT_MAX;
        for (int right = 0; right < n; right++) {
            curSum += nums[right];
            while (curSum >= target) {
                res = min(res, right - left + 1);
                curSum -= nums[left];
                left++;
            }
        }
        return res == INT_MAX ? 0 : res;
    }
};