递归基础练习-1
1、求和
1 package com.wangymd.recursive; 2 3 /** 4 * @desc 数组递归求和 5 * @author wangymd 6 * @data 2022-07-03 15:35:13 7 */ 8 public class SumTest { 9 10 public static void main(String[] args) { 11 int[] array1 = { 1, 2, 3, 4, 5, 6, 7, 8}; 12 System.out.println(sum(array1, 0)); 13 } 14 15 public static int sum(int[] array, int index) { 16 if (index == array.length) { 17 return 0; 18 } else { 19 return array[index] + sum(array, index + 1); 20 } 21 } 22 }
2、数组是否排序判断
1 package com.wangymd.recursive; 2 3 /** 4 * @desc 数组是否有序递归 5 * @author wangymd 6 * @data 2022-07-03 15:33:55 7 */ 8 public class ArrayIsSortedTest { 9 10 public static void main(String[] args) { 11 int[] array1 = { 1, 2, 3, 4, 5 }; 12 System.out.println(isSorted(array1, array1.length, "asc")); 13 int[] array2 = { 1, 2, 3, 6, 5 }; 14 System.out.println(isSorted(array2, array2.length, "asc")); 15 16 int[] array3 = { 5, 4, 3, 2, 1 }; 17 System.out.println(isSorted(array3, array3.length, "desc")); 18 int[] array4 = { 5, 4, 3, 4, 1 }; 19 System.out.println(isSorted(array4, array4.length, "desc")); 20 } 21 22 public static boolean isSorted(int[] array, int index, String type) { 23 if (index == 1) { 24 return true; 25 } 26 27 if("desc".equalsIgnoreCase(type)){ 28 return array[index - 1] >= array[index - 2] ? false : isSorted(array, index - 1, type); 29 }else if("asc".equalsIgnoreCase(type)){ 30 return array[index - 1] <= array[index - 2] ? false : isSorted(array, index - 1, type); 31 }else{ 32 return false; 33 } 34 } 35 }
3、阶乘
1 package com.wangymd.recursive; 2 3 /** 4 * @desc 递归 5 * @author wangymd 6 * @data 2022-07-03 15:32:53 7 */ 8 public class FactorialTest { 9 10 public static void main(String[] args) { 11 System.out.println(factorial(6)); 12 } 13 14 /** 15 * 递归阶乘 16 * @param n 17 * @return 18 */ 19 public static int factorial(int n) { 20 if(n == 0) { 21 return 1; 22 }else { 23 return n * factorial(n - 1); 24 } 25 } 26 }
4、汉诺塔
①
1 package com.wangymd.recursive; 2 3 /** 4 * @desc 递归 https://blog.csdn.net/question_mark/article/details/100907008 5 * @author wangymd 6 * @data 2022-07-03 15:35:37 7 */ 8 public class HanoiTest { 9 10 public void hanoi(int n, char A, char B, char C) { 11 if (n == 1) { 12 move(A, C);//最大的圆盘从A移动到C 13 return; 14 } 15 hanoi(n - 1, A, C, B);//C为辅助 16 move(A, C); 17 hanoi(n - 1, B, A, C);//A为辅助 18 } 19 20 private void move(char A, char C) { 21 System.out.println("move: " + A + "----->" + C); 22 } 23 24 public static void main(String[] args) { 25 HanoiTest hanoiTest = new HanoiTest(); 26 hanoiTest.hanoi(4, 'A', 'B', 'C');//移动A到C 27 } 28 }
②
1 package com.wangymd.recursive; 2 3 import java.util.Stack; 4 5 /** 6 * @desc 递归 https://blog.csdn.net/question_mark/article/details/100907008 7 * @author wangymd 8 * @data 2022-07-03 15:36:32 9 */ 10 public class HanoiTest2 { 11 12 public static Stack<Integer> hanoiA = new Stack<Integer>(); 13 public static Stack<Integer> hanoiB = new Stack<Integer>(); 14 public static Stack<Integer> hanoiC = new Stack<Integer>(); 15 16 public static Integer times = 0; 17 18 public void hanoi(int n, Stack<Integer> A, Stack<Integer> B, Stack<Integer> C) { 19 if (n == 1) { 20 move(A, C);//最大的圆盘从A移动到C 21 return; 22 } 23 hanoi(n - 1, A, C, B);//C为辅助,n-1移动到B 24 move(A, C);//A最下面的移动到C 25 hanoi(n - 1, B, A, C);//A为辅助，B上n-1个移动到C 26 } 27 28 private void move(Stack<Integer> A, Stack<Integer> C) { 29 System.out.println("<<<<<<<<第" + (++times) + "移动>>>>>>>>"); 30 C.push(A.pop()); 31 System.out.println("移动后hanoiA:" + hanoiA + " ,hanoiB:" + hanoiB + " ,hanoiC:" + hanoiC); 32 } 33 34 public static void main(String[] args) { 35 HanoiTest2 hanoiTest = new HanoiTest2(); 36 37 hanoiA.push(1); 38 hanoiA.push(2); 39 hanoiA.push(3); 40 hanoiA.push(4); 41 hanoiA.push(5); 42 hanoiA.push(6); 43 44 System.out.println("移动前hanoiA:" + hanoiA); 45 hanoiTest.hanoi(hanoiA.size(), hanoiA, hanoiB, hanoiC);//移动A到C 46 System.out.println("移动完成hanoiC:" + hanoiC); 47 } 48 }
