LeetCode-in-Java

209. Minimum Size Subarray Sum

Medium

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

public class Solution {
    public int minSubArrayLen(int target, int[] nums) {
        int i = 0;
        int j = 0;
        int sum = 0;
        int min = Integer.MAX_VALUE;
        while (j < nums.length) {
            sum += nums[j];
            if (sum >= target) {
                while (i <= j) {
                    if (sum - nums[i] >= target) {
                        sum = sum - nums[i];
                        i++;
                    } else {
                        break;
                    }
                }
                if (j - i + 1 < min) {
                    min = j - i + 1;
                }
            }
            j++;
        }
        if (min == Integer.MAX_VALUE) {
            return 0;
        }
        return min;
    }
}

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