[剑指offer] JAVA版题解 面试题49

代码演示：

package swordfingeroffer; /** * <p>Description: </p> * * @author 罗志远 * @version 1.0 * @name InterviewQuestion49 * @date 2020-07-04 10:29 */ public class InterviewQuestion49 { private boolean isUgly(int number) { while (0 == number % 2) { number /= 2; } while (0 == number % 3) { number /= 3; } while (0 == number % 5) { number /= 5; } return 1 == number ? true : false; } public int getUglyNumber(int index) { if (index <= 0) { throw new RuntimeException("参数不能小于或者等于0！"); } int number = 0; int uglyIndex = 0; while (uglyIndex < index) { number ++; if (isUgly(number)) { uglyIndex ++; } } return number; } // 已空间换时间的解法 public int getUglyNumber2(int index) { if (index <= 0) { throw new RuntimeException("参数不能小于或者等于0！"); } int[] result = new int[index]; int t2 = 0; int t3 = 0; int t5 = 0; result[0] = 1; for (int i = 1; i < index; i ++) { result[i] = Math.min(Math.min(result[t2] * 2,result[t3] * 3), result[t5] * 5); if (result[i] == result[t2] * 2) { t2 ++; } if (result[i] == result[t3] * 3) { t3 ++; } if (result[i] == result[t5] * 5) { t5 ++; } } return result[index - 1]; } }