从一个数组中查找和目标数最近的或者相等的数

大疆无人机笔试题，二分法求解：

#include <iostream>
#include <stdlib.h>
#include <math.h>
#include <stdio.h>
using namespace std;
int binarySearchKey(int *arr,int goal,int len)
{
    int i;
    for(i = 0;i < len;++i)
    {
        cout<<arr[i]<<" ";
    }
    int targetindex = 0;
    int left = 0,right = 0;
    for(right = len - 1; left != right;)
    {
        int midIndex = (right + left)/2;
        int mid = (right - left);
        int midValue = arr[midIndex];
        if(goal == midValue)
        {
            return midIndex;
        }
        if(goal > midValue)
        {
            left = midIndex;
        }
        else
        {
            right = midIndex;
        }
        if(mid <= 1)
        {
            break;
        }
    }
    int rightnum = arr[right];
    int leftnum = arr[left];
    int ret = abs((rightnum - leftnum)/2) > abs(rightnum -goal) ? rightnum : leftnum;
    return ret;
}
int main()
{
    int a[8] = {0,1,2,3,5,6,8,9};
    int k = binarySearchKey(a,4,8);
    cout<<"k = " << k <<endl;
}