JAVA实现二分查找

                北京时间2022年03月13日,晚22:06分。天气晴朗，多云，温度28。今天来实现JAVA二分查找，二分查找的前提是数组有序，核心思想是比较target和array[mid]的关系,如果target大于array[mid]就到右边找,反之到左边找。实现方式有两种：递归实现以及迭代实现。

（一）、代码实现：

public static void main(String[] args){
    int[] array = {0,1,2,3,4,5,6,7};
    int[] arrays = {-99,-98,1,3,4,11,15,17};
    int index = RecursiveFind(arrays,-111,0,7);
//    int indexs = IteratorFind(arrays,-999);
    System.out.println("index = "+index);
//    System.out.println("indexs = "+indexs);
}
/**
 * 递归实现
 */
public static int RecursiveFind(int[] array,int target,int start,int end){
    int mid = (end+start)/2;
    if (start>end || 0>end){
        return -1;
    }
    if (target>array[mid]){
        return RecursiveFind(array,target,mid+1,end);
    }else if (target<array[mid]){
        return RecursiveFind(array,target,start,mid-1);
    }else if (target==array[mid]){
        return mid;
    }else {
        return -1;
    }
}
/**
 * 迭代实现
 */
public static int IteratorFind(int[] array,int target){
    int left = 0;
    int right = array.length-1;
    // 迭代实现使用while循环
    while (left<=right){
        int mid = (right+left)/2;
        if (target>array[mid]){
            left = mid+1;
        }else if (target<array[mid]){
            right = mid-1;
        }else {
            return mid;
        }
    }
    return -1;
}