https://leetcode-cn.com/problems/shortest-unsorted-continuous-subarray/

problem

Given an integer array nums, you need to find one continuous subarray that if you only sort this subarray in ascending order, then the whole array will be sorted in ascending order.

Return the shortest such subarray and output its length.

example

Example 1:

Input: nums = [2,6,4,8,10,9,15]
Output: 5
Explanation: You need to sort [6, 4, 8, 10, 9] in ascending order to make the whole array sorted in ascending order.

Example 2:

Input: nums = [1,2,3,4]
Output: 0

Example 3:

Input: nums = [1]
Output: 0

Constraints:

1 <= nums.length <= 104
-105 <= nums[i] <= 105

solution

/**
* from n-1 find last lo  rightPart less than lo;
* from 0  find last hi  leftpart larger than b,
*/ 
class Solution {
    public int findUnsortedSubarray(int[] nums) {
        int n = nums.length;
        int rightMin = Integer.MAX_VALUE;
        int lo = -1;
        for (int i = n-1 ;i >= 0; i--) {
            if( nums[i] > rightMin ) {
                lo = i;
            } else {
                rightMin = nums[i];
            }
        }

        if ( lo == -1) {
            return 0;
        }

        int leftMax = Integer.MIN_VALUE;
        int hi = -1;
        for (int i = 0 ; i < n; i++) {
            if (nums[i] < leftMax) {
                hi = i;
            } else {
                leftMax = nums[i];
            }
        }
        return hi - lo + 1;
    }
}