Lintcode 406. Minimum Size Subarray Sum

Given an array of n positive integers and a positive integer s, find the minimal length of a subarray of which the sum ≥ s. If there isn't one, return -1 instead.

Example

Example 1:

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

Example 2:

Input: [1, 2, 3, 4, 5], s = 100
Output: -1

Challenge

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

Code (Java):

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public class Solution {     /**      * @param nums: an array of integers      * @param s: An integer      * @return: an integer representing the minimum size of subarray      */     public int minimumSize(int[] nums, int s) {         if (nums == null || nums.length == 0) {             return -1;         }                   int minLen = Integer.MAX_VALUE;         int sum = 0;         int left = 0;                   for (int right = 0; right < nums.length; right++) {             sum += nums[right];                           while (sum >= s) {                 minLen = Math.min(minLen, right - left + 1);                 sum -= nums[left];                 left++;             }         }                   return minLen == Integer.MAX_VALUE ? -1 : minLen;     } }