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q*02012-02-28 08:02

1 楼

See the code below. I am confused that "len = 5" from main function, "len =
4" from RemoveDuplicate function. When does terminate '\0' count? Thanks.
#include
using namespace std;
void RemoveDuplicate(char str[])
{
int len = sizeof(str)/sizeof(str[0]);
cout << "len = " << len << endl;
}
int main()
{
char a[] = "abcd";
int len = sizeof(a)/sizeof(a[0]);
cout << "len = " << len << endl;
RemoveDuplicate(a);
return 0;
}

l*a2012-02-28 08:02

2 楼

please use "abcde" as your input and check the result

=

【在 q******0 的大作中提到】

: See the code below. I am confused that "len = 5" from main function, "len =
: 4" from RemoveDuplicate function. When does terminate '\0' count? Thanks.
: #include
: using namespace std;
: void RemoveDuplicate(char str[])
: {
: int len = sizeof(str)/sizeof(str[0]);
: cout << "len = " << len << endl;
: }
: int main()

i*e2012-02-28 08:02

3 楼

Try this and figure out why:
void foo(int str[])
{
int len = sizeof(str)/sizeof(str[0]);
cout << "len = " << len << endl;
}
int main()
{
int a[] = {1,2,3,4};
int len = sizeof(a)/sizeof(a[0]);
cout << "len = " << len << endl;
foo(a);
return 0;
}

r*k2012-02-28 08:02

4 楼

void RemoveDuplicate(char str[])
{
int len = sizeof(str)/sizeof(str[0]);
cout << "len = " << len << endl;
}
这上面这段code中，sizeof(str)是计算“the size of the pointer represented by
the array identifier”, which is always 4.

S*I2012-02-28 08:02

5 楼

not necessarily always 4; size of a pointer is implementation defined.

by

【在 r*****k 的大作中提到】

: void RemoveDuplicate(char str[])
: {
: int len = sizeof(str)/sizeof(str[0]);
: cout << "len = " << len << endl;
: }
: 这上面这段code中，sizeof(str)是计算“the size of the pointer represented by
: the array identifier”, which is always 4.

r*k2012-02-28 08:02

6 楼

Yes, you are right. I meant that in lz's test case, it's always 4.

【在 S**I 的大作中提到】

: not necessarily always 4; size of a pointer is implementation defined.
:
: by

a*a2012-02-28 08:02

7 楼

...not

【在 r*****k 的大作中提到】

: Yes, you are right. I meant that in lz's test case, it's always 4.

p*i2012-02-28 08:02

8 楼

If you are on a 64bit environment and compiles the source code in 64bit mode
, the main function will output len = 5 (length of the C string) and the
RemoveDuplicate function will output len=8, which is exactly sizeof(char*)/
sizeof(char)

=

【在 q******0 的大作中提到】