Super Ugly Number
描述
Write a function to find the n
-th super ugly number.
Super ugly numbers are positive numbers whose all prime factors are in the given prime list primes
of size k
. For example, [1, 2, 4, 7, 8, 13, 14, 16, 19, 26, 28, 32]
is the sequence of the first 12 super ugly numbers given primes = [2, 7, 13, 19]
of size 4.
Note:
- 1 is a super ugly number for any given
primes
. - The given numbers in
primes
are in ascending order. - 0 <
k
≤ 100, 0 <n
≤ 1000000, 0 <primes[i]
< 1000.
分析
这题是 Ugly Number II 的扩展。在"Ugly Number II"中,primes=[2,3,5]
,这题中primes
可以自由变化。
所以这题可以用"Ugly Number II"的思路解决。每次要从多个列表中选择最小的元素,我们可以维护一个大小为primes
长度的小根堆。