二分查找

#include <iostream>
using namespace std;
int binarySearch(int *a, int low, int high, int key)
{
    int mid;
    while(low <= high){
        mid = (low + high)/2;
        if(key > a[mid])
            low = mid + 1;
        else
            if(key < a[mid])
                high = mid - 1;
            else
                return mid;
    }
    return -1;
}
int main()
{
    int a[] = {1,3,5,7,9,11};
    cout << binarySearch(a, 0, 6, 3) << endl;
    cout << binarySearch(a, 0, 6, 0) << endl;
    cout << "Hello world!" << endl;
    return 0;
}