java递归写重写查询以及反转数组
java写两个方法,具体如下,一个是查询方法,一个是reverseArrayToString. 都需要用递归来写
public class ReverseArray {
public static void swap(int[] A, int a, int b){
int temp;
temp = A[a];
A[a] = A[b];
A[b] = temp;
}
public static void reverseArray(int A[], int start, int end){
if(start == end || start > end){
return;
}
if(start < end){
swap(A,start, end);
}
reverseArray(A, ++start, --end);
}
public static void main(String[] args){
int[] A = {1,2,3,4,5,6,7,8,9};
reverseArray(A, 0, A.length - 1);
printArray.printArrayint(A);
}
}
package com.example.demo003.controller;
public class Test04 {
public static boolean search(int item, int[] arr, int start) {
if (arr == null) {
throw new IllegalArgumentException();
}
if (arr.length - 1 == start && arr[start] != item) {
return false;
}
if (arr[start] == item) {
return true;
} else {
return search(item, arr, ++start);
}
}
public static void main(String[] args) {
System.out.println(search(1, new int[]{3, 4, 1}, 0));
System.out.println(search(1, new int[]{1, 2, 3}, 1));
System.out.println(search(5, new int[]{3, 4, 1}, 0));
}
}
package com.example.demo003.controller;
public class test05 {
public static String reverseArray(String[] arr, int index) {
if (arr == null)
return "";
if (index == arr.length / 2 - 1 && arr.length % 2 == 0) {
return arr[arr.length - 1 - index] + "," + arr[index];
}
if (index == arr.length / 2 && arr.length % 2 == 1) {
return arr[index];
}
return (index == 0 ? "[" : "") + arr[arr.length - 1 - index] + "," + reverseArray(arr, index + 1) + "," + arr[index] + (index == 0 ? "]" : "");
}
public static void main(String[] args) {
System.out.println(reverseArray(new String[]{"abc", "def", "hig"}, 0));
System.out.println(reverseArray(new String[]{"abc", "def", "hig", "lmn"}, 0));
}
}