962. Maximum Width Ramp

Given an array A of integers, a ramp is a tuple (i, j) for which i < j and A[i] <= A[j]. The width of such a ramp is j - i.

Find the maximum width of a ramp in A. If one doesn't exist, return 0.

Example 1:

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

Example 2:

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

Note:

1. 2 <= A.length <= 50000
2. 0 <= A[i] <= 50000

# @lc code=start
using LeetCode

function max_width_ramp(A::Vector{Int})
    res = 0
    stk = [1]
    for i in 2:length(A)
        (A[i] < A[stk[end]]) && (push!(stk, i))
    end
    for i in length(A):-1:2
        idx = i
        while !isempty(stk) && A[stk[end]] <= A[i]
            idx = pop!(stk)
        end
        res = max(i - idx, res)
    end
    return res
end
# @lc code=end

max_width_ramp (generic function with 1 method)

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