581. Shortest Unsorted Continuous Subarray

Given an integer array, 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, too.

You need to find the shortest such subarray and output its length.

Example 1:

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

Note:

1. Then length of the input array is in range [1, 10,000].
2. The input array may contain duplicates, so ascending order here means <=.

先找到最左边的降序对以及最右边的降序对，之后有一种情况是在left和right中间可能存在比left左边小或者比right右边大的数字，这样的话还需要扩展边界，因此找到[left, right]中的最大值和最小值之后扩展边界。

class Solution {public:    int findUnsortedSubarray(vector<int>& nums) {        if(nums.size() <= 1) return 0;        int left = 0, right = nums.size() - 1;        while(left < nums.size() - 1 && nums[left] <= nums[left + 1]) left++;         if(left == nums.size() - 1) return 0;        while(nums[right] >= nums[right - 1]) right --;                int lmax = INT_MIN, rmin = INT_MAX;        for(int i = left; i <= right; ++ i){            if(nums[i] > lmax) lmax = nums[i];            if(nums[i] < rmin) rmin = nums[i];        }        while(left >= 0 && nums[left] > rmin) left--;        while(right < nums.size() && nums[right] < lmax) right++;                return right - left - 1;    }};