[leetcode-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: 5
Explanation: You need to sort [6, 4, 8, 10, 9] in ascending order to make the whole array sorted in ascending order.
Note:
Then length of the input array is in range [1, 10,000].
The input array may contain duplicates, so ascending order here means <=.

思路：

用一个map记录初始每一个位置对应的数字，排序后，再从两头依次判断是否是原来的数字。

int findUnsortedSubarray(vector<int>& nums)
     {         
         map<int, int>record;
         for (int i = 0; i < nums.size();i++)  record[i] = nums[i];
         
         sort(nums.begin(), nums.end());
         int start = 0, end = nums.size()-1;
         while (start< nums.size() && nums[start] == record[start]) start++;
         while (end >start && nums[end] == record[end]) end--;
         return end - start + 1;
     }