排序

1.二分查找

public class test {
     public static void main(String[]  args) {
 //        定义数组
         int[] arr  ={81,51,88,15,59,20,1,50,66,77,4};
 //        对数组进行升序排序
         Arrays.sort(arr);
 //        打印数组
          System.out.println(Arrays.toString(arr));
 //        打印查找结果
          System.out.println(binarySearch(arr,59));
     }
     public static int  binarySearch(int[]arr,int value){
         int low = 0;
         int high = arr.length-1;
 //        循环直到不能再分
         while (low<=high){
             int mid = (low+high)/2;
             if (value == arr[mid]){
 //                返回匹配值的下标
                 return mid;
             }
             if (value < arr[mid]){
                 high = mid-1;
             }
             if (value > arr[mid]){
                 low = mid+1;
             }
 
         }
 //        如果没有查找到值，则返回404
         return 404;
     }
 }

2.冒泡排序

public class demo_sort {
    public static void main(String[] args) {
        //冒泡排序算法
        int[] numbers=new int[]{1,5,8,2,3,9,4};
        //需进行length-1次冒泡
        for(int i=0;i<numbers.length-1;i++)
        {
            for(int j=0;j<numbers.length-1-i;j++)
            {
                if(numbers[j]>numbers[j+1])
                {
                    int temp=numbers[j];
                    numbers[j]=numbers[j+1];
                    numbers[j+1]=temp;
                }
            }
        }
        System.out.println("从小到大排序后的结果是:");
        for(int i=0;i<numbers.length;i++)
            System.out.print(numbers[i]+" ");
    }