264. Ugly Number II

Write a program to find the n-th ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5.

Example:

Input: n = 10
Output: 12
Explanation:1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugly numbers.

Note:

1. 1 is typically treated as an ugly number.
2. n does not exceed 1690.

# @lc code=start
using LeetCode

function nth_ugly_number(n::Int)
    dp = Vector{Int}(undef, n)
    p2 = p3 = p5 = dp[1] = 1
    for i in 2:n
        nums = dp[p2] * 2, dp[p3] * 3, dp[p5] * 5
        dp[i] = minimum(nums)
        p2 += dp[i] == nums[1]
        p3 += dp[i] == nums[2]
        p5 += dp[i] == nums[3]
    end
    return dp[n]
end
# @lc code=end

nth_ugly_number (generic function with 1 method)

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