Java 查找算法

package com.lin.search_0303;

import java.util.ArrayList;
import java.util.List;

public class BinarySearch {

    public static void main(String[] args) {
        int arr[] = { 1, 8, 10, 89, 1000, 1234 ,1234, 1234};
        int index = binarySearch(arr, 0, arr.length-1, 0);
        System.out.println(index);
        ArrayList<Integer> resList = binarySearchAll(arr, 0, arr.length-1, 12342);
        if(resList.size()!=0) {
            for (Integer integer : resList) {
                System.out.println(integer);
            }
        } else {
            System.out.println("没有找到");
        }
        
        
    }
    
    
    /**
     * 
     * @Description:二分查找 
     * @author LinZM  
     * @date 2021-3-3 21:38:42 
     * @version V1.8
     * @param arr 数组
     * @param left 左边索引
     * @param right 右边索引
     * @param findVal 要查找的值
     * @return 如果找到就返回下标，如果没有找到就返回-1
     */
    public static int binarySearch(int[] arr, int left, int right, int findVal) {
        
        // 当left>right时，说明递归整个数组都没有找到该值
        if(left>right) {
            return -1;
        }
        int mid = (left+right)/2;
        int midVal = arr[mid];
        
        if(findVal > midVal) { // 向右递归
            return binarySearch(arr, mid+1, right, findVal);
        } else if(findVal < midVal) {
            return binarySearch(arr, left, mid-1, findVal);
        } else{
            return mid;
        } 
    }
    
    // 可以找到多个相同的值，同时返回下标
public static ArrayList<Integer> binarySearchAll(int[] arr, int left, int right, int findVal) {
        
        // 当left>right时，说明递归整个数组都没有找到该值
        if(left>right) {
            return new ArrayList<Integer>();
        }
        int mid = (left+right)/2;
        int midVal = arr[mid];
        
        if(findVal > midVal) { // 向右递归
            return binarySearchAll(arr, mid+1, right, findVal);
        } else if(findVal < midVal) {
            return binarySearchAll(arr, left, mid-1, findVal);
        } else{
            ArrayList<Integer> resIndex = new ArrayList<Integer>();
            int temp = mid-1;
            while(true) {
                if(temp < 0 || arr[temp] != findVal) {
                    break;
                }
                resIndex.add(temp);
                temp -= 1;
            }
            
            resIndex.add(mid);
            
            temp = mid+1;
            while(true) {
                if(temp > arr.length-1 || arr[temp] != findVal) {
                    break;
                }
                resIndex.add(temp);
                temp += 1;
            }
            return resIndex;
        } 
    }
}