[Leetcode] #313 Super Ugly Number

Discription

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 integer.

Solution

int nthSuperUglyNumber(int n, vector<int>& primes) {
	vector<int> ugly(n, INT_MAX);
	ugly[0] = 1;
	vector<int> index(primes.size(), 0);
	for (int i = 1; i < n; i++){
		for (int j = 0; j < primes.size();j++){
			if (ugly[index[j]] * primes[j] < ugly[i]){
				ugly[i] = ugly[index[j]] * primes[j];
			}				
		}
		for (int j = 0; j < primes.size(); j++){
			index[j] += (ugly[i] == ugly[index[j]] * primes[j]);
		}
	}
	return ugly[n - 1];
}

GitHub-Leetcode:https://github.com/wenwu313/LeetCode