数组的二分查找

执行二分查找的前提：这个数组必须是有序的。

package com.demo.sort;

public class BinarySearch {
    /**
    * 二分查找算法
    *
    * @param srcArray 有序数组
    * @param des 查找元素
    * @return des的数组下标，没找到返回-1
    */
    
    //循环
    public static int binarySearch(int[] srcArray, int des) {
        int left = 0;
        int right = srcArray.length - 1;
        while (left <= right) {
            int middle = (left + right) / 2;
            if (des == srcArray[middle]) {
                return middle;
            } else if (des < srcArray[middle]) {
                right = middle - 1;
            } else {
                left = middle + 1;
            }
        }
        return -1;
    }
    
    //递归
     public static int binSearch(int srcArray[], int start, int end, int key) {   
            int mid = (end - start) / 2 + start;   
            if (srcArray[mid] == key) {   
                return mid;   
            }   
            if (start >= end) {   
                return -1;   
            } else if (key > srcArray[mid]) {   
                return binSearch(srcArray, mid + 1, end, key);   
            } else if (key < srcArray[mid]) {   
                return binSearch(srcArray, start, mid - 1, key);   
            }   
            return -1;   
        } 
    
    public static void main(String[] args){
        int[] src = new int[] { 1, 3, 5, 7, 8, 9 };
        System.out.println(binarySearch(src, 9));
    }

}