费式数列问题
package algorithm.fibonacci;import java.util.ArrayList;import java.util.Arrays;import java.util.List;public class RabbitService {class Rabbit {public int age;public Rabbit() {this.age = 1;}public Rabbit(int age) {this.age = age;}}/* * 面向对象方法 */public void printRabbit(int month, int bearAge) {if (month > 0) {long start = System.currentTimeMillis();// 保存每个月份的兔子数目long[] rabbitNumbersArray = new long[month];// rabbitList保存所有的兔子,在第一个月有一对大兔子Rabbit bigRabbit = new Rabbit();List<Rabbit> rabbitList = new ArrayList<Rabbit>();rabbitList.add(bigRabbit);rabbitNumbersArray[0] = rabbitList.size();// 从第二个月开始计算，如果兔子刚生下来age为1，则age为3时兔子才能生兔子for (int currentMonth = 2; currentMonth <= month; currentMonth++) {int lastMonthRabbitNumber = rabbitList.size();for (int i = 0; i < lastMonthRabbitNumber; i++) {Rabbit rabbit = rabbitList.get(i);rabbit.age++;if (rabbit.age >= bearAge) {rabbitList.add(new Rabbit());}}rabbitNumbersArray[currentMonth - 1] = rabbitList.size();}long end = System.currentTimeMillis();System.out.println("1月到" + month + "月的兔子数目为："+ Arrays.toString(rabbitNumbersArray) + ",使用时间为"+ (end - start));} else {System.out.println("输入月份必须大于0");}}/* * 作用递归方法计算费式数列,当兔子生育月不为3时，也可以计算 */public void printRabbit2(int month, int bearAge) {if (month > 0) {long start = System.currentTimeMillis();long[] rabbitNumbersArray = new long[month];for (int i = 1; i <= month; i++) {rabbitNumbersArray[i - 1] = fibonacci(i, bearAge);}long end = System.currentTimeMillis();System.out.println("1月到" + month + "月的兔子数目为："+ Arrays.toString(rabbitNumbersArray) + ",使用时间为"+ (end - start));} else {System.out.println("输入月份必须大于0");}}private int fibonacci(int n, int bearAge) {if (n < bearAge) {return 1;} else {return fibonacci(n - 1, bearAge)+ fibonacci(n - (bearAge - 1), bearAge);}}/* * 根据费式数列特点，当前值为前两项之和 */public void printRabbit3(int month, int bearAge) {if (month > 0) {long start = System.currentTimeMillis();long[] rabbitNumbersArray = new long[month];int currentMonth = 0;for (currentMonth = 1; currentMonth < bearAge; currentMonth++) {rabbitNumbersArray[currentMonth - 1] = 1;}for (currentMonth = bearAge; currentMonth <= month; currentMonth++) {rabbitNumbersArray[currentMonth - 1] = rabbitNumbersArray[currentMonth- bearAge]+ rabbitNumbersArray[currentMonth - 2];}long end = System.currentTimeMillis();System.out.println("1月到" + month + "月的兔子数目为："+ Arrays.toString(rabbitNumbersArray) + ",使用时间为"+ (end - start));} else {System.out.println("输入月份必须大于0");}}public static void main(String[] args) {RabbitService service = new RabbitService();int bearAge = 3;service.printRabbit(20, bearAge);service.printRabbit2(20, bearAge);service.printRabbit3(20, bearAge);}}
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输出：
1月到20月的兔子数目为：[1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765],使用时间为61月到20月的兔子数目为：[1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765],使用时间为21月到20月的兔子数目为：[1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765],使用时间为0
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