503. Next Greater Element II

Given a circular array (the next element of the last element is the first element of the array), print the Next Greater Number for every element. The Next Greater Number of a number x is the first greater number to its traversing-order next in the array, which means you could search circularly to find its next greater number. If it doesn't exist, output -1 for this number.

Example 1:

Input: [1,2,1]
Output: [2,-1,2]
Explanation: The first 1's next greater number is 2; The number 2 can't find next greater number; The second 1's next greater number needs to search circularly, which is also 2.

Note: The length of given array won't exceed 10000.

# @lc code=start
using LeetCode

function next_greater_elements(nums::Vector{Int})
    stk = Int[]
    res = fill(-1, size(nums))
    for rd in 1:2, (idx, num) in enumerate(nums)
        while !isempty(stk) && nums[stk[end]] < num
            res[pop!(stk)] = num
        end
        (rd == 1) && push!(stk, idx)
    end
    return res
end
# @lc code=end

next_greater_elements (generic function with 1 method)

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