Today I have done leetcode's October LeetCoding Challenge with cpp.

October LeetCoding Challenge 10

Description

Maximum Width Ramp

A ramp in an integer array nums is a pair (i, j) for which i < j and nums[i] <= nums[j]. The width of such a ramp is j - i.

Given an integer array nums, return the maximum width of a ramp in nums. If there is no ramp in nums, return 0.

Example 1:

Input: nums = [6,0,8,2,1,5]
Output: 4
Explanation: The maximum width ramp is achieved at (i, j) = (1, 5): nums[1] = 0 and nums[5] = 5.

Example 2:

Input: nums = [9,8,1,0,1,9,4,0,4,1]
Output: 7
Explanation: The maximum width ramp is achieved at (i, j) = (2, 9): nums[2] = 1 and nums[9] = 1.

Constraints:

• 2 <= nums.length <= 5 * 104
• 0 <= nums[i] <= 5 * 104

Solution

class Solution {
public:
  int maxWidthRamp(vector<int>& nums) {
    vector<int> st;
    int answer = 0;
    int n = nums.size();
    for(int i = 0; i < n; ++i) {
      if(st.empty() || nums[st.back()] > nums[i]) {
        st.push_back(i);
      }
    }
    for(int i = n - 1; i > answer; --i) {
      while(st.size() && nums[st.back()] <= nums[i]) {
        answer = max(answer, i - st.back());
        st.pop_back();
      }
    }
    return answer;
  }
};