LeetCode 209 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
0 instead.

For example, given the array 

[2,3,1,2,4,3]

 and 

s
= 7

,

the subarray 

[4,3]

 has the minimal length under the problem constraint.

click to show more practice.

More practice:
If you have figured out the O(n) solution, try coding another solution of which the time complexity is O(n log n).
Runtime: 1
ms

O(n)
time, O(1) space moving window method
using a moving window [left,i] to calculate the sum, first move i forward to get a sub-array with sum>=s, then move left forward to
make sum < s, then move end again,..., until i reach the end of array.

public int minSubArrayLen(int s, int[] nums) {
int min = Integer.MAX_VALUE, left = 0;
for (int i = 0; i < nums.length; i++) {
s -= nums[i];
while (s <= 0) {
min = Math.min(min, i - left + 1);
s += nums[left++];
}
}
return min == Integer.MAX_VALUE ? 0 : min;
}