/**

* 测试递归recursion

*/

public class TestRecursion2 {

public static int m = 0;

public static int factorial(int n){

// factorial 阶乘

m++;

if (m<n){

return m*factorial(n);

}else{

m = 0;

return n;

}

}

public static void main(String[] args) {

System.out.println(factorial(10));

System.out.println(10*9*8*7*6*5*4*3*2);

}

}

class TestRecursion3{

//计算 斐波那契数列 [1,2,3,5,8,13,21…..]每一位是前两位的和

public static int abc(int n) {

//计算第n位的值

if (n > 2) {

return abc(n – 1) + abc(n – 2);

} else if (n==2) {

return 2;

}else return 1;

}

public static int def(int n){

if (n<2){

return 1;

}else if (n<3){

return 2;

}

int a1 = 1;

int a2 = 2;

int result = a1+a2;

for (int i =4;i<=n;i++){

a1 = a2;

a2 = result;

result = a1+a2;

}

return result;

}

public static int ghi(int n){

if (n<2){

return 1;

}else if (n<3){

return 2;

}

int[] arr = new int[n];

arr[0] = 1;

arr[1] = 2;

for (int i=2;i<n;i++){

arr[i] = arr[i-1]+arr[i-2];

}

return arr[n-1];

}

public static void main(String[] args) {

int n = new Random().nextInt(20)+1;

System.out.println(n);

System.out.println(abc(n));

System.out.println(def(n));

System.out.println(ghi(n));

}

}