Super Ugly Number

Desicription

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.

Example:

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Input: n = 12, primes = [2,7,13,19]
Output: 32
Explanation: [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 is a super ugly number for any given primes.
  • The given numbers in primes are in ascending order.
  • 0 < k ≤ 100, 0 < n ≤ 106, 0 < primes[i] < 1000.
  • The nth super ugly number is guaranteed to fit in a 32-bit signed integer.

Solution

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class Solution {
public:
int nthSuperUglyNumber(int n, std::vector<int>& primes) {
auto index = std::vector<int>(primes.size(), 0);
auto uglys = std::vector<int>(n, INT_MAX);
uglys[0] = 1;

for(auto& ugly : uglys) {
for(int i = 0; i < index.size(); i++) {
ugly = std::min(ugly, uglys[index[i]] * primes[i]);
}
for(int i = 0; i < index.size(); i++) {
if(ugly == uglys[index[i]] * primes[i]) {
index[i]++;
}
}
}

return uglys[uglys.size() - 1];
}
};