[leetcode 263 264]Ugly Number I 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.

Credits:

Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

AC代码：

class Solution {
public:
    bool isUgly(int num) {
        if(num==0)
            return false;
        while(num!=1)
        {
            if(num%2==0)
                num=num/2;
            else if(num%3==0)
                num=num/3;
            else if(num%5==0)
                num=num/5;
            else
                break;
        }
        return num==1;
    }
};

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

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5.
For example, 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugly
numbers.

Note that 1 is typically treated as an ugly number.

当然是用I中的判断函数一个数字一个数字的判断也是可以的，但是时间效率就不高了

AC代码：

class Solution
{
public:

    int minNum(int x,int y)
    {
        return x<y?x:y;
    }

    int nthUglyNumber(int n)
    {
        if(n==0)
            return 0;
        int *count=new int[n];
        count[0]=1;
        int two=0;
        int three=0;
        int five=0;
        int sum=1;
        int min=0;
        while(sum<n)
        {
            min=minNum(minNum(count[two]*2,count[three]*3),count[five]*5);
            if(min>count[sum-1])
            {
                count[sum]=min;
                ++sum;
            }
            if(min==count[two]*2)
                ++two;
            else if(min==count[three]*3)
                ++three;
            else
                ++five;
        }
        return count[sum-1];
    }
};

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