查找——BinarySearch

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int b_search(int *a, int n, int value)
{
    int low = 0;
    int high = n-1;
    while (low < high)
    {
        int mid = (low+high)/2;
        if (a[mid] == value)
        {
            return mid;
        }
        else if (a[mid] > value)
        {
            high = mid - 1;
        }
        else
        {
            low = mid + 1;
        }
    }
    return -1;
}