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Test34.java
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140 lines (119 loc) · 3.68 KB
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/**
* Author: 王俊超
* Date: 2015-06-11
* Time: 14:35
* Declaration: All Rights Reserved !!!
*/
public class Test34 {
/**
* 判断一个数是否只有2，3，5因子（丑数）
*
* @param num 待判断的数，非负
* @return true是丑数，false丑数
*/
private static boolean isUgly(int num) {
while (num % 2 == 0) {
num /= 2;
}
while (num % 3 == 0) {
num /= 3;
}
while (num % 5 == 0) {
num /= 5;
}
return num == 1;
}
/**
* 找第index个丑数，速度太慢
*
* @param index 第index个丑数
* @return 对应的丑数值
*/
public static int getUglyNumber(int index) {
if (index <= 0) {
return 0;
}
int num = 0;
int uglyFound = 0;
while (uglyFound < index) {
num++;
if (isUgly(num)) {
++uglyFound;
}
}
return num;
}
/**
* 找第index个丑数，【第二种方法】
*
* @param index 第index个丑数
* @return 对应的丑数值
*/
public static int getUglyNumber2(int index) {
if (index <= 0) {
return 0;
}
int[] pUglyNumbers = new int[index];
pUglyNumbers[0] = 1;
int nextUglyIndex = 1;
int p2 = 0;
int p3 = 0;
int p5 = 0;
while (nextUglyIndex < index) {
int min = min(pUglyNumbers[p2] * 2, pUglyNumbers[p3] * 3, pUglyNumbers[p5] * 5);
pUglyNumbers[nextUglyIndex] = min;
while (pUglyNumbers[p2] * 2 <= pUglyNumbers[nextUglyIndex]) {
p2++;
}
while (pUglyNumbers[p3] * 3 <= pUglyNumbers[nextUglyIndex]) {
p3++;
}
while (pUglyNumbers[p5] * 5 <= pUglyNumbers[nextUglyIndex]) {
p5++;
}
nextUglyIndex++;
}
return pUglyNumbers[nextUglyIndex - 1];
}
private static int min(int n1, int n2, int n3) {
int min = n1 < n2 ? n1 : n2;
return min < n3 ? min : n3;
}
public static void main(String[] args) {
System.out.println("Solution 1:");
test1();
System.out.println();
System.out.println("Solution 2:");
test2();
}
private static void test1() {
System.out.println(getUglyNumber(1)); // 1
System.out.println(getUglyNumber(2)); // 2
System.out.println(getUglyNumber(3)); // 3
System.out.println(getUglyNumber(4)); // 4
System.out.println(getUglyNumber(5)); // 5
System.out.println(getUglyNumber(6)); // 6
System.out.println(getUglyNumber(7)); // 8
System.out.println(getUglyNumber(8)); // 9
System.out.println(getUglyNumber(9)); // 10
System.out.println(getUglyNumber(10)); // 12
System.out.println(getUglyNumber(11)); // 15
System.out.println(getUglyNumber(1500)); // 859963392
System.out.println(getUglyNumber(0)); // 0
}
private static void test2() {
System.out.println(getUglyNumber2(1)); // 1
System.out.println(getUglyNumber2(2)); // 2
System.out.println(getUglyNumber2(3)); // 3
System.out.println(getUglyNumber2(4)); // 4
System.out.println(getUglyNumber2(5)); // 5
System.out.println(getUglyNumber2(6)); // 6
System.out.println(getUglyNumber2(7)); // 8
System.out.println(getUglyNumber2(8)); // 9
System.out.println(getUglyNumber2(9)); // 10
System.out.println(getUglyNumber2(10)); // 12
System.out.println(getUglyNumber2(11)); // 15
System.out.println(getUglyNumber2(1500)); // 859963392
System.out.println(getUglyNumber2(0)); // 0
}
}