Lintcode 620. Maximum Subarray IV

Given an integer arrays, find a contiguous subarray which has the largest sum and length should be greater or equal to given length k.
Return the largest sum, return 0 if there are fewer than k elements in the array.

Example

Example 1:

Input:
[-2,2,-3,4,-1,2,1,-5,3]
5
Output:
5
Explanation:
[2,-3,4,-1,2,1]
sum=5

Example 2:

Input:
[5,-10,4]
2
Output:
-1

Notice

1. Ensure that the result is an integer type.
2. k > 0

Code (Java):

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public class Solution {     /**      * @param nums: an array of integer      * @param k: an integer      * @return: the largest sum      */     public int maxSubarray4(int[] nums, int k) {         // write your code here         if (nums == null || nums.length < k) {             return 0;         }                   int[] minPresum = new int[nums.length + 1];         int sum = 0;         int maxSum = Integer.MIN_VALUE;                   for (int i = 1; i <= nums.length; i++) {             sum += nums[i - 1];             minPresum[i] = Math.min(minPresum[i - 1], sum);                           if (i >= k) {                 maxSum = Math.max(maxSum, sum - minPresum[i - k]);             }         }                   return maxSum;     } }