UGLY NUMBER II

Write a program to find the n-th ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5.

Example:

Input: n = 10
Output: 12
Explanation: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugly numbers.

Note:

1 is typically treated as an ugly number. n does not exceed 1690.

Solution:

class Solution {
public:
    unsigned getNthUglyNo(unsigned n) 
    { 
        unsigned ugly[n]; 
        unsigned i2 = 0, i3 = 0, i5 = 0; 
        unsigned next_multiple_of_2 = 2; 
        unsigned next_multiple_of_3 = 3; 
        unsigned next_multiple_of_5 = 5; 
        unsigned next_ugly_no = 1; 
        ugly[0] = 1; 
        for (int i=1; i<n; i++) 
        { 
           next_ugly_no = min(next_multiple_of_2,min(next_multiple_of_3,next_multiple_of_5)); 
           ugly[i] = next_ugly_no; 
           if (next_ugly_no == next_multiple_of_2) 
           { 
               i2 = i2+1; 
               next_multiple_of_2 = ugly[i2]*2; 
           } 
           if (next_ugly_no == next_multiple_of_3) 
           { 
               i3 = i3+1; 
               next_multiple_of_3 = ugly[i3]*3; 
           } 
           if (next_ugly_no == next_multiple_of_5) 
           { 
               i5 = i5+1; 
               next_multiple_of_5 = ugly[i5]*5; 
           } 
        }
        return next_ugly_no; 
    } 
    int nthUglyNumber(int n) {
        return getNthUglyNo(n);
    }
};