[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
;
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];
}
};

其他Leetcode题目AC代码：https://github.com/PoughER/leetcode