ceil函数：返回大于或者等于指定表达式的最小整数

floor函数：返回计算不大于给定值的最大整数

#include<stdio.h>
#include<math.h>
int main(void)
{double number=123.45;double down,up;down=floor(number);up=ceil(number);printf("originalnumber%5.2lf\n",number);printf("numberroundeddown%5.2lf\n",down);printf("numberroundedup%5.2lf\n",up);return 0;
}

完全二叉树：

完全二叉树的深度是log2(n+1)向上取整；代码：ceil(log(n+1)/log(2))
log(a) b=log © b÷log © a (换底公式)