【重点】a += b执行速度更快
2*0.5,因为0.5的精度更高,所以运算结果的精度要和0.5一样。
位数太多采用高精度算法,位运算。
double d = a/b; //先算出a/b=3,再将3赋值给d,d=3.
d = (double)a/b; //先将a转化为double双精度型,然后再运算,运算结果依精度高的,因此(double)a/b=3.33333
#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
int a = 10;
int b = 3;
double d = a/b;
cout << d << endl;//3
d = 5/2;//5/2=2
cout << d << endl;//2
d = 5/2.0;//5/2.0=2.5;
cout << d << endl;//2.5
d = (double)a/b;
cout << d << endl;//3.33333
return 0;
}
#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
int n1 , n2 = 5;
n2 ++;//n2=6
++ n2;//n2=7
n1 = n2 ++;//n1=n2=7,n2自增1等于8
cout << n1 << "," << n2 << endl;//7,8
n1 = ++ n2;//n2自增1等于9,n1=n2=9;
cout << n1 << "," << n2 << endl;//9,9
return 0;
}