【算法 · 二分查找】学会的第一个小算法

package OOP_;

public class day_01 {
    public static void main(String[] args) {
        System.out.println();

        int[] arr = {0,5,18,11,900,12,4,9,7,2,8,3,6};
        SortAndSearch sas = new SortAndSearch();
        System.out.println("排序后的数组为：");
        sas.sort(arr);
        System.out.println();
        int result = sas.search(arr,5);
        if(result != -1)
            System.out.println("查到该数，其下标为：" + result);
        else
            System.out.println("查无此数");

    }
}

class SortAndSearch{
    public void sort(int[] arr){
        for(int i = 0;i < arr.length - 1;i++){
            for(int j = 0;j < arr.length - i - 1; j++){
                if(arr[j] > arr[j+1]){
                    int temp = arr[j + 1];
                    arr[j + 1] = arr[j];
                    arr[j] = temp;
                }
            }
        }

        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + "t");
        }
    }

    public int search(int[] arr, int target){
        int first = 0;
        int last = arr.length - 1;
        while(first <= last){
            int mid = (first + last) >> 1;
            if(target > arr[mid]){
                first = mid + 1;
            }else if(target < arr[mid]){
                last = mid - 1;
            }else if(target == arr[mid]){
                return mid;
            }
        }
        return -1;
    }

}