[英]Program crashes when `if (variable % 2 == 0)`
I'm writing a program that finds perfect numbers . 我正在写一个寻找完美数字的程序。 Having read about these perfect numbers I came across a list of them: List of perfect numbers .
阅读完这些理想数字后,我发现了其中的一个列表: 理想数字列表 。 At the moment the output is:
目前的输出是:
28 // perfect
496 // perfect
8128 // perfect
130816 // not perfect
2096128 // not perfect
33550336 // perfect
I decided to create array and put it with numbers, which divide the number wholly (without the rest). 我决定创建一个数组,并将其放入数字中,该数字将整个数字相除(不包括其余部分)。 So I will be able to verify if it is a perfect number or not by adding all elements of the array.
因此,通过添加数组的所有元素,我将能够验证它是否为完美数。 But app crashes and I cannot understand why:
但是应用程序崩溃了,我不明白为什么:
#include <stdio.h>
#include <stdlib.h>
int main()
{
unsigned long number;
unsigned long arr2[100] = {0};
int k = 0;
for ( number = 0; number <= 130816; number++ )
if ( 130816 % number == 0 )
arr2[k++] = number;
for ( k = 0; k < 100; k++ )
printf("%lu", arr2[k]);
return 0;
}
You are doing modulus zero
here: 您在这里将模数设为
zero
:
if ( 130816 % number == 0 )
which is undefined behavior. 这是未定义的行为。 If you start your for loop at
1
instead it should fix that issue. 如果您从
1
开始for循环,则应该可以解决该问题。 However, since N % 1 == 0
for all N
, you probably need to start at 2
. 但是,由于所有
N
N % 1 == 0
,您可能需要从2
开始。
From the C99
standard, 6.5.5 /5
(unchanged in C11
): 根据
C99
标准6.5.5 /5
(在C11
更改):
The result of the / operator is the quotient from the division of the first operand by the second;
/运算符的结果是第一个操作数除以第二个的商。 the result of the % operator is the remainder.
%运算符的结果是余数。 In both operations, if the value of the second operand is zero, the behavior is undefined.
在这两个操作中,如果第二个操作数的值为零,则行为是不确定的。
You are dividing by zero when number=0; 当number = 0时,您被零除;
138816 % number
involves division and a remainder. 138816 % number
涉及除法和余数。
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