二分查找算法

#include <iostream>
using namespace std;

//二分查找
int binary_search(int* a, int len, int goal);

int main()
{
    const int LEN = 10000;
    int a[LEN];
    for (int i = 0; i < LEN; i++)
        a[i] = i - 5000;
    int target = 0;
    int index = binary_search(a, LEN, target);

    if (index != -1)
        cout<<target<<"在数组中的下标为"<<index<<endl;
    else
        cout<<"不存在"<<target<<endl;
    return 0;
}

int binary_search(int* a, int len, int goal)
{
    int low = 0;
    int high = len -1;
    while (low <= high)
    {
        int middle = (high - low) / 2 + low; // 直接使用(high + low) / 2 可能导致溢出
        if (a[middle] == goal)
            return middle;
        //在左半边
        else if (a[middle] > goal)
            high = middle - 1;
        //在右半边
        else
            low = middle + 1;
    }
    //没找到
    return -1;
}