1 /*************************************************************************
2 > File Name: 32_UglyNumber.c
3 > Author: Juntaran
4 > Mail: JuntaranMail@gmail.com
5 > Created Time: 2016年09月02日 星期五 12时29分59秒
6 ************************************************************************/
7
8 #include <stdio.h>
9 #include <malloc.h>
10
11 int isUgly(int number)
12 {
13 while (number % 2 == 0)
14 number /= 2;
15 while (number % 3 == 0)
16 number /= 3;
17 while (number % 5 == 0)
18 number /= 5;
19
20 return (number==1) ? 0 : -1;
21 }
22
23 // 低效方法
24 int getUglyNumber1(int n)
25 {
26 if (n <= 0)
27 return -1;
28
29 int number = 0;
30 while (n != 0)
31 {
32 ++ number;
33 if (isUgly(number) == 0)
34 n --;
35 }
36 printf("%d\n", number);
37 return number;
38 }
39
40 int MinOfThree(int a, int b, int c)
41 {
42 int minNum = a>b ? b : a;
43 minNum = minNum>c ? c : minNum;
44 return minNum;
45 }
46
47 // 高效方法 空间换时间
48 int getUglyNumber2(int index)
49 {
50 if (index <= 1)
51 return index;
52
53 int* ugly = (int*)malloc(sizeof(int) * index);
54 int i2 = 0;
55 int i3 = 0;
56 int i5 = 0;
57 ugly[0] = 1;
58
59 for (int i = 1; i < index; ++i)
60 {
61 int temp2 = ugly[i2] * 2;
62 int temp3 = ugly[i3] * 3;
63 int temp5 = ugly[i5] * 5;
64
65 int minNum = MinOfThree(temp2, temp3, temp5);
66 ugly[i] = minNum;
67
68 if (minNum == temp2)
69 i2 ++;
70 if (minNum == temp3)
71 i3 ++;
72 if (minNum == temp5)
73 i5 ++;
74 }
75 printf("%d\n", ugly[index - 1]);
76 return ugly[index - 1];
77 }
78
79 int main()
80 {
81 getUglyNumber1(1500);
82 getUglyNumber2(1500);
83 }
