LeetCode 313. Super Ugly Number（超级丑的数字）

原题网址：https://leetcode.com/problems/super-ugly-number/

Write a program to find the nth 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)

1

is a super ugly number for any given

primes

.

(2) The given numbers in

primes

are in ascending order.

(3) 0 <

k

≤ 100, 0 <

n

≤
106, 0 <

primes[i]

<
1000.
方法：动态规划+最小堆。

public class Solution {
public int nthSuperUglyNumber(int n, int[] primes) {
if (n<=1) return 1;
int[] nums = new int
;
nums[0] = 1;
int[] pos = new int[primes.length];
PriorityQueue<Integer> minHeap = new PriorityQueue<>(new Comparator<Integer>() {
@Override
public int compare(Integer i1, Integer i2) {
return Integer.compare(nums[pos[i1]] * primes[i1], nums[pos[i2]] * primes[i2]);
}
});
for(int i=0; i<primes.length; i++) minHeap.add(i);
for(int i=1; i<n; i++) {
do {
int min = minHeap.poll();
nums[i] = nums[pos[min]] * primes[min];
pos[min] ++;
minHeap.offer(min);
} while (nums[i]==nums[i-1]);
}
return nums[n-1];
}
}