二分查找的递归和非递归实现

Posted 2022-12-03 yinhuanxu

public class BinarySearch 


    //非递归
    public static int binSearch1(int[] arr, int target) 
        if(arr == null || arr.length == 0)
            return -1;
        int left = 0, right = arr.length - 1;
        while(left <= right) 
            int mid = (left + right) / 2;
            if(arr[mid] == target) 
                return mid;
            
            if(arr[mid] < target) 
                left = mid + 1;
            
            if(arr[mid] > target) 
                right = mid - 1;
            
        
        return -1;
    

    //递归
    public static int binSearch2(int[] arr, int target, int left, int right) 
        if(arr == null || arr.length == 0)
            return -1;
        if(left > right) 
            return -1;
        
        int mid = (left + right) / 2;
        if(arr[mid] == target) 
            return mid;
        
        if(arr[mid] > target) 
            return binSearch2(arr, target, left, mid-1);
        
        if(arr[mid] < target) 
            return binSearch2(arr, target, mid+1, right);
        
        return -1;
    



    public static void main(String[] args) 
        int[] testArr = new int[]1,2,3,5,8,9,12,13,15,20;
        System.out.println(binSearch1(testArr, 3));
        System.out.println(binSearch2(testArr, 3, 0, 10));