The given solution is a quadratic time solution. Here is a linear time solution:

#include <iostream>
#include <vector>
using namespace std;

class Solution {
public:
    int findMaxLength(const vector<int>& nums) {
        stack<int> goodStartPos;
        goodStartPos.push(0);

        for(int i = 1; i < nums.size(); i++){
            int prevIdx = goodStartPos.top();
            if(nums[i]>nums[prevIdx]){
                goodStartPos.push(i);
            }
        }

        int maxLength = 0;

        for(int i = nums.size()-1; i>=0; i--){
            while(!goodStartPos.empty() && nums[goodStartPos.top()]>nums[i]){
                maxLength = max(maxLength, i - goodStartPos.top() + 1);
                goodStartPos.pop();
            }
        }
        return maxLength;
    }
};