Ugly Number Ugly Number II

Write a program to check whether a given number is an ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.

Note that 1 is typically treated as an ugly number.

bool isUgly(int num) {
    if(num <= 0)
        return false;
    while(num % 2 == 0)
        num /= 2;
    while(num % 3 == 0)
        num /= 3;
    while(num % 5 == 0)
        num /= 5;
    return num == 1;
}

Ugly Number II

 

劍指offer -醜數

int Min(int num1,int num2,int num3)
{
    int min = (num1 < num2) ? num1:num2;
    min = (min < num3) ?min:num3;
    return min;
}
int nthUglyNumber(int n) {
    if(n <= 0)
        return 0;
    int ugly[n];
    ugly[0] = 1;
    int index = 1;
    int *p2 = ugly;
    int *p3 = ugly;
    int *p5 = ugly;
    while(index < n)
    {
        int min = Min(*p2 * 2,*p3 * 3,*p5 * 5);
        ugly[index] = min;
        
        while(*p2 * 2 <= ugly[index])
            ++p2;
        while(*p3 * 3 <= ugly[index])
            ++p3;        
        while(*p5 * 5 <= ugly[index])
            ++p5;        
        
        
        ++index;
        
    }
    return ugly[index - 1];
}