c++ - 将 long long 除以 int 会遇到什么问题？

Question

什么是执行除法的更安全的方法:

long long/int 还是 long long/(long long) int？

将 long long 除以 int 时，是否会存在一些安全问题或任何逻辑问题？

Answer 1

On dividing a long long by an int, can there be some security issues or any logical issues?

答案是NO，前提是你的分母不为 0。

来自文档:

Many binary operators that expect operands of arithmetic or enumeration type cause conversions and yield result types in a similar way. The purpose is to yield a common type, which is also the type of the result. This pattern is called the usual arithmetic conversions, which are defined as follows:

• If either operand is of type long double, the other shall be converted to long double.
• Otherwise, if either operand is double, the other shall be converted to double.
• Otherwise, if either operand is float, the other shall be converted to float.
• Otherwise, the integral promotions (4.5) shall be performed on both operands.
• Then, if either operand is unsigned long the other shall be converted to unsigned long.
• Otherwise, if one operand is a long int and the other unsigned int, then if a long int can represent all the values of an unsigned int, the unsigned int shall be converted to a long int; otherwise both operands shall be converted to unsigned long int.
• Otherwise, if either operand is long, the other shall be converted to long.
• Otherwise, if either operand is unsigned, the other shall be converted to unsigned.

[Note: otherwise, the only remaining case is that both operands are int]

那就是

int / int => returns int

float / float => returns float

double /double => returns double

int / double => returns double

int / float => returns float