#include<stdio.h>
#include<windows.h>
int main()
{
	//本質是向0取整
   //trunc()函數也有這種作用，不過返回值是浮點數，而且必須引用math.h頭文件
	int i = -2.9;
	int j = 2.9;
	printf("%d\n", i); //結果是：-2
	printf("%d\n", j); //結果是：2
	system("pause");
	return 0;
}

#include <stdio.h>
#include <math.h> //因為使用了floor函數，需要添加該頭文件
#include <windows.h>
int main()
{
	//本質是向-∞取整，注意輸出格式要不然看不到結果
	printf("%.1f\n", floor(-2.9)); //-3
	printf("%.1f\n", floor(-2.1)); //-3
	printf("%.1f\n", floor(2.9)); //2
	printf("%.1f\n", floor(2.1)); //2
	system("pause");
	return 0;
}

#include <stdio.h>
#include <math.h>
#include <windows.h>
int main()
{
	//本質是向+∞取整，注意輸出格式要不然看不到結果
	printf("%.1f\n", ceil(-2.9)); //-2
	printf("%.1f\n", ceil(-2.1)); //-2
	printf("%.1f\n", ceil(2.9)); //3
	printf("%.1f\n", ceil(2.1)); //3
	system("pause");
	return 0;
}

#include <stdio.h>
#include <math.h>
#include <windows.h>
int main()
{
//本質是四舍五入
printf("%.1f\n", round(2.1));
printf("%.1f\n", round(2.9));
printf("%.1f\n", round(-2.1));
printf("%.1f\n", round(-2.9));
system("pause");
return 0;
}

#include <stdio.h>
#include <math.h>
#include <windows.h>
int main()
{
	const char* format = "%.1f \t%.1f \t%.1f \t%.1f \t%.1f\n";
	printf("value\tround\tfloor\tceil\ttrunc\n");
	printf("-----\t-----\t-----\t----\t-----\n");
	printf(format, 2.3, round(2.3), floor(2.3), ceil(2.3), trunc(2.3));
	printf(format, 3.8, round(3.8), floor(3.8), ceil(3.8), trunc(3.8));
	printf(format, 5.5, round(5.5), floor(5.5), ceil(5.5), trunc(5.5));
	printf(format, -2.3, round(-2.3), floor(-2.3), ceil(-2.3), trunc(-2.3));
	printf(format, -3.8, round(-3.8), floor(-3.8), ceil(-3.8), trunc(-3.8));
	printf(format, -5.5, round(-5.5), floor(-5.5), ceil(-5.5), trunc(-5.5));
	system("pause");
	return 0;
}

#include<stdio.h>
#include <windows.h>
int main()
{
	printf("%d\n", -10 / 3); //結果：-3
	printf("%d\n\n", -10 % 3); //結果：-1 為什么? -10=(-3)*3+(-1)
	printf("%d\n", 10 / -3); //結果：-3
	printf("%d\n\n", 10 % -3); //結果：1 為什么？10=(-3)*(-3)+1
	system("pause");
	return 0;
}