Given an integer array nums, return the length of the shortest contiguous subarray such that sorting only that subarray in nondecreasing order makes the entire array nums sorted in nondecreasing order. If nums is already sorted in nondecreasing order, return $0$.

Note: Follow up: can you solve it in $O(n)$ time complexity?

Constraints:

• $1 \leq$ nums.length $\leq 10^4$

• $-10^5 \leq$ nums[i] $\leq 10^5$

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