整数二分查找模板

//第一个,区间被划分成[1, mid], [mid + 1, r]

int bsearch_1(int l, int r)
{
    while (l < r)
    {
        int mid = l + r >> 1;
        if (check(mid)) r = mid;    //判断mid是否满足性质
        else l = mid + 1;
    }
    return l;
}

//第二个,区间被划分成[1, mid - 1], [mid , r]

int bsearch_2(int l, int r)
{
    while (l < r)
    {
        int mid = l + r + 1 >> 1;
        if (check(mid)) l = mid;
        else r = mid - 1;
    }
    return l;
}