如果想学透二分查找的话，可以看我的另一篇博客：https://blog.csdn.net/weixin_42110638/article/details/83376472
package zuoye4; //import java.util.Scanner; import java.util.Arrays; public class Main { public static void main(String[] args) { // TODO Auto-generated method stub int []arr = {1,6,2,4,9,8,7,3}; Arrays.sort(arr,0,arr.length);//sort(int[] a, int fromIndex, int toIndex) // 对指定 int 型数组的指定范围按数字升序进行排序。 for(int i = 0;i < arr.length;i++) { if(i==0) System.out.print(arr[i]); else System.out.print(" "+arr[i]); } System.out.println(); array t = new array(); System.out.println(t.efdiguifa(arr, 9, 0, arr.length));//测试递归 System.out.println(); System.out.println(t.efxunhuanfa(arr,9, 0, arr.length));//测试循环 } } package zuoye4; public class array { public int efdiguifa(int []a,int x,int start,int end)//递归法 { int mid = start + (end - start)/2; if(start >= end) return -1;//查找完毕没有找到答案，返回-1 else { if(a[mid] == x) return mid; else if(a[mid] > x) return efdiguifa(a,x,start,mid-1);//往左找 else return efdiguifa(a,x,mid+1,end);//往右找 } } public int efxunhuanfa(int []a,int x,int start,int end)//循环法 { // 这里必须是 <= while (start <= end) { int mid = (start + end) / 2; if (a[mid] == x) { return mid; } else if (a[mid] < x) { start = mid + 1; } else { end = mid - 1; } } return -1; } }
