编辑代码

#include <stdio.h>
#include <math.h>
int main()
{   
    printf("一、观察round函数\n");
    printf("1.1 一位小数:保留一位小数\n");
    printf("round(2.5)=%.1f\n", round(2.5));//结果是3.0
    printf("round(3.5)=%.1f\n", round(3.5));//结果是4.0,round函数返回的是浮点型的整数
    printf("round(-2.5))=%.1f\n", round(-2.5));//结果是-3.0
    printf("round(-3.5))=%.1f\n\n\n", round(-3.5));//结果是-4.0,看来只看正数部分

    printf("1.2 两位小数:保留一位小数\n");
    printf("小数部分0.45:\n");
    printf("round(2.45))=%.1f\n", round(2.45));//结果是2.0
    printf("round(3.45))=%.1f\n", round(3.45));//结果是3.0
    printf("round(-2.45))=%.1f\n", round(-2.45));//结果是-2.0
    printf("round(-3.45))=%.1f\n\n", round(-3.45));//结果是-3.0,看来不到0.5不进位

    printf("小数部分大于0.45:\n");
    printf("round(2.47))=%.1f\n", round(2.47));
    printf("round(3.47))=%.1f\n", round(3.47));
    printf("round(-2.47))=%.1f\n", round(-2.47));
    printf("round(-3.48))=%.1f\n\n", round(-3.48));//不到0.5不进位

    printf("小数部分接近0.5:\n");
    printf("round(2.499999999))=%.1f\n", round(2.499999999));
    printf("round(3.499999999))=%.1f\n", round(3.499999999));
    printf("round(-2.499999999))=%.1f\n", round(-2.499999999));
    printf("round(-3.499999999))=%.1f\n\n", round(-3.499999999));//非常接近0.5也不行,不进位

    printf("查看数据类型匹配和不匹配的情况:\n");
    printf("%d\n", round(-3.45));//round(-3.45))返回的是浮点型的整数
    printf("%f\n", 45);//不匹配
    printf("%d\n", 90.5);//不匹配
    printf("%d\n", 85555);//匹配

    return 0;
}