313. 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.
(4) The nth super ugly number is guaranteed to fit in a 32-bit signed intege

dp[i]表示第i个超级丑数，index[i]表示primes[i]应该与dp数组的哪一个相乘。

public class Solution {    public int nthSuperUglyNumber(int n, int[] primes) {        int[] dp=new int[n];        int[] index=new int[primes.length];        int i=1;        dp[0]=1;        while(i<n){            int min=Integer.MAX_VALUE,minindex=0;            for(int j=0;j<primes.length;j++){                if(dp[index[j]]*primes[j]<min){                    min=dp[index[j]]*primes[j];                    minindex=j;                }            }            index[minindex]++;            if(dp[i-1]!=min){                dp[i++]=min;            }        }        return dp[n-1];    }}