2021-03-18

二分查找：
package demo05;

public class erfen {
public static void main(String[] args) {
int[] arr={1,3,5,7,9};
int key=7;
int i = binarySearch(arr, key);
System.out.println(i);

}
public static int binarySearch(int[] arr1, int key){

    int min=0;
    int max=arr1.length-1;
    while(min<=max){
        //中间索引
        int mid=(min+max)/2;
        if(key > arr1[mid]){
            min = mid+1;
        }else if(key < arr1[mid]){
            max = mid-1;
        }else{
            return mid;
        }
    }
    return -1;
}

}

运行结果：