Shortest Unsorted Continuous Subarray

Jin Shang bio photo By Jin Shang

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.


  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 <=.


Two pass, one from left and one from right.

On left, update the current max, any element that is less than current max is the left end of this subarray.

class Solution {
    int findUnsortedSubarray(vector<int>& nums) {
        int cmin = INT_MAX;
        int cmax = INT_MIN;
        int st = 1, nd = 0;
        int l = 0;
        int r = nums.size()-1;
            if(nums[l] >= cmax){
                cmax = nums[l];
                nd = l;
            if(nums[r] <= cmin){
                cmin = nums[r];
                st = r;
        return nd-st+1;