程序代码：

int element_count(int * set, int len, int e)
{
    int f, a, b, t;
    for(a = 0, b = len - 1; a < b; set[t = a + b >> 1] <  e ? (a = t + 1) : (b = t));
    for(f = a, b = len - 1; a < b; set[t = a + b >> 1] <= e ? (a = t + 1) : (b = t));
    return b - f;
}

程序代码：

int element_count(int * set, int len, int e)
{
    int t;
    if(set[0] == e && set[len - 1] == e) return len;
    if(set[0] > e || set[len - 1] < e) return 0;
    t = len / 2;
    return element_count(set, t, e) + element_count(set + t, len - t, e);
}