581. Shortest Unsorted Continuous Subarray

begin,end必须初始化，如果整个数组是排序好的，经过for循环后，begin、end还是原始的值。

注意：end必须比begin小1，因为最终的长度是end - begin + 1，关键在于这个+1的地方

class Solution {
public:
    int findUnsortedSubarray(vector<int>& nums) {
        int length = nums.size();
        if(length <= 0)
            return 0;
        int max_num = nums[0],min_num = nums[length-1];
        int begin = 0,end = -1;
        for(int i = 0;i < length;i++){
            if(nums[i] > max_num)
                max_num = nums[i];
            if(nums[length-1-i] < min_num)
                min_num = nums[length-1-i];
            if(nums[i] < max_num)
                end = i;
            if(nums[length-1-i] > min_num)
                begin = length-1-i;
        }
        return end - begin + 1;
    }
};

https://www.cnblogs.com/jimmycheng/p/7673733.html