随手敲代码——二分法

二分法:讲道理的说,我还是改了好几次才写好- -

package com.kevindai;

import java.util.Arrays;

public class BinarySearch {

    public static void main(String[] args) {
        int[] source =  {1,8,15,7,95,30,78,32,56,91,17};
        Arrays.sort(source);

        int key = 8;
        System.out.println(rank(source,key));

    }

    public static int rank(int a[],int key){
        int start = 0;
        int end = a.length - 1;
        while(start <= end){
            int mid = start + (end - start)/2;
            if(a[mid] > key){
                end = mid - 1;
            }else if(a[mid] < key){
                start = mid + 1;
            }else{
                return mid;
            }
        }

        return -1;
    }
}

看到这里有人要问了,我直接用以下代码不是更简单

for(int i = 0;i < arr.length;i++){ if(arr[i] == key){ return key; }
}

我真是飞上去一脚,就你知道的多!用二分法快啊、效率高啊、会写别人不会写的东西B格高啊!