209. Minimum Size Subarray Sum

难度: Medium

题目描述

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:

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] <= 104

 

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)).

解题思路

代码实现

解决方案

java

class Solution {
    public int minSubArrayLen(int target, int[] nums) {
        
        int left = 0;
        int sum = 0;
        int min = Integer.MAX_VALUE;
        for (int right = 0; right < nums.length; right++) {
            sum += nums[right];
            while (sum >= target) {
                min = Math.min(min, right - left+1);
                sum -= nums[left];
                left++;
            }
        }

        return min==Integer.MAX_VALUE?0:min;
    }
}