How do I get the length of an array in C + +?

C, C + + does not provide direct access to the array length of the function, for the character array holding the string provides a strlen function to get the length, then for other types of arrays how to get their length? One method is to use sizeof (array)/sizeof (array[0]), which is used in C to define it as a macro, such as # define Get_array_len (Array,len) {LEN = (sizeof ( Array)/sizeof (array[0]);} 。 In C + +, you can use template technology to define a function, such as:

Template <class t>

int Getarraylen (t& array)

{

Return (sizeof (array)/sizeof (array[0));

}

This allows you to use this macro or this function to get the length of the array for different types of arrays. Here are two demo programs, a C language, and a C + +:

P.S: If the array is an array of characters that store strings, then the length to be calculated also needs to be reduced by one, that is, the definition of macro: #define Get_array_len (array,len) {LEN = (sizeof (ARRAY)/sizeof (array[0])-1); }, for function definitions:

Template <class t>

int Getarraylen (t& array)

{

Return (sizeof (array)/sizeof (array[0])-1);

}

The reason is that the character array that stores the string has a ' + ' character at the end, and it needs to be removed.

"C Language"

#include <stdio.h>

#include <stdlib.h>

#define Get_array_len (array,len) {LEN = (sizeof (ARRAY)/sizeof (array[0));}

Define a macro with parameters to store the length of the array in the variable len

int main ()

{

Char a[] = {' 1 ', ' 2 ', ' 3 ', ' 4 '};

int Len;

Get_array_len (A,len)

Call a predefined macro to get the length of array A and store it in the variable len

printf ("%d\n", Len);

System ("pause");

return 0;

}

"C + +"

#include <iostream>

using namespace Std;

Template <class t>

int Getarraylen (t& array)

{//using a template to define a function Getarraylen, the function returns the length of an array of arrays

Return (sizeof (array)/sizeof (array[0));

}

int main ()

{

Char a[] = {' 1 ', ' 2 ', ' 3 '};

cout << Getarraylen (a) << Endl;

return 0;

}
Another: in C + + functions, if an array is passed in as a parameter, then the array will degenerate into a pointer, so it is not known the length of the array (the array here refers to static rather than new).

This article from Csdn Blog, reproduced please indicate the source: http://blog.csdn.net/bopzhou/archive/2010/12/08/6063163.aspx

How do I get the length of an array in C + +?