2289. Steps to Make Array Non-decreasing

You are given a 0-indexed integer array nums. In one step, remove all elements nums[i] where nums[i - 1] > nums[i] for all 0 < i < nums.length.

Return the number of steps performed until nums becomes a non-decreasing array.

c++

class Solution {
public:
    int totalSteps(vector<int>& nums) {
        int res = 0, n = nums.size();
        vector<pair<int, int>> st;
        for(int i = n - 1; i >= 0; i--) {
            int count = 0;
            while(!st.empty() and st.back().first < nums[i]) {
                count = max(count + 1, st.back().second);
                st.pop_back();
            }
            res = max(res, count);
            st.push_back({nums[i], count});
        }
        return res;
    }
};