313. Super Ugly Number

313. Super Ugly Number          

Write a program 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) 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 n^th super ugly number is guaranteed to fit in a 32-bit signed integer.

        这道题目也是Ugly Number 的变形，只是之前的题目中primes数组是确定的[2，3，5]，这道题把primes数组变成了一个变量，但是思路与Ugly Number Ⅱ 是一摸一样的。

class Solution { public: int nthSuperUglyNumber(int n, vector<int>& primes) { vector<int> m(n); m[0] = 1; vector<int> t(primes.size(), 1); vector<int> index(primes.size(), 0); int i=0; while (++i < n) { m[i] = t[0] * primes[0]; for (int j = 0; j < primes.size(); j++) { if (m[i] > t[j] * primes[j]) { m[i] = t[j] * primes[j]; } } for (int j = 0; j < primes.size(); j++) { if (m[i] == t[j] * primes[j]) { t[j] = m[++index[j]]; } } } return m[n - 1]; } };