[leetcode] Super Ugly Number

题目：

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.

分析：具体解析过程可参考Ugly Number II，Java代码如下：

    public int minAll(int[] factors) {
        int min = factors[0];
        for(int f : factors) {
            if(f < min) {
                min = f;
            }
        }
        return min;
    }
    public int nthSuperUglyNumber(int n, int[] primes) {
        int[] factors = new int[primes.length];
        System.arraycopy(primes, 0, factors, 0, primes.length);
        int[] index = new int[primes.length];
        int[] uglyNums = new int[n];
        uglyNums[0] = 1;
        for(int i = 1; i < n; i++) {
            int min = minAll(factors);
            uglyNums[i] = min;
            for(int k = 0; k < factors.length; k++) {
                if(min == factors[k]) {
                    factors[k] = primes[k] * uglyNums[++index[k]];
                }
            }
        }
        return uglyNums[n-1];
    }