String Array Count

Question

below is my code. i know its a very simple problem but i dont know why this code is not working. i simply want to count number of strings in my array but its always showing me a count 1.

#include<stdio.h>
#include<string.h>

int main()
{
    char *str[]={"Bharti","Bharat","Akas"};
    int a=PalindromeLengthPuzzle(str);
    return 0;
}
int PalindromeLengthPuzzle(char* input1[])
{
    //const char *mystr=input1;
    int i;
    int sarray= sizeof(input1)/sizeof(input1[0]);
    printf("%s",input1[0]);
    //int sarray=sizeof(mystr)/sizeof(mystr[0]);
    //int x=sizeof(mystr[0]);
    printf("%d",sarray);
    //printf("%s",input1[1]);
    /*for( i=0;i<sarray;i++)
    {
    printf("%s",input1[i]);
    }*/
    return 0;
}

Output of the above code is Bharti1 and it should be 3 instead of 1. Any help would be grateful.

Sadique · Answer 1 · 2015-04-17T09:37:56.573

2

Change your code to:

#include<stdio.h>
#include<string.h>

int main()
{
    char *str[]={"Bharti","Bharat","Akas"};
    int a=PalindromeLengthPuzzle(str, sizeof(str)/sizeof(str[0]));
    return 0;
}
int PalindromeLengthPuzzle(char* input1[], int sarray)
{
    //const char *mystr=input1;
    int i;
    printf("%s",input1[0]);
    //int sarray=sizeof(mystr)/sizeof(mystr[0]);
    //int x=sizeof(mystr[0]);
    printf("%d",sarray);
    //printf("%s",input1[1]);
    /*for( i=0;i<sarray;i++)
    {
    printf("%s",input1[i]);
    }*/
    return 0;
}

Arrays decay into pointers in methods hence you cannot calculate the size inside the function - rather pass the size in function call.

edited Apr 17 '15 at 09:37

answered Apr 17 '15 at 09:34

Sadique

22,572
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Actually in the function `PalindromeLengthPuzzle()` i am not suppose to pass anything else. Is there any other alternative ? – G.S Abhaypal Apr 17 '15 at 09:37
1

Then make the variable `sarray` Global. – Sadique Apr 17 '15 at 09:38

Vlad from Moscow · Accepted Answer · 2015-04-17T10:03:10.503

0

When an array passed to a function as an argument it implicitly converted to a pointer to its first element.

Thus these three function declarations are equivalent

int PalindromeLengthPuzzle(char* input1[3]);
int PalindromeLengthPuzzle(char* input1[]);
int PalindromeLengthPuzzle(char** input1);

and declare the same one function.

Within the function the parameter is a local variable of type char **

So statement

int sarray= sizeof(input1)/sizeof(input1[0]);

is equivalent to

int sarray= sizeof( char ** )/sizeof( char * );

and evaluates to 1.

You should either declare a second parameter that will contain the number of elements in the array or us some sentinel value as for example NULL as the last velement of the array that within the functionto determine the number of elements by using this sentinel.

Here are demonstrated the two approaches

#include<stdio.h>
#include<string.h>

int PalindromeLengthPuzzle( char* input1[], size_t n )
{
   // ...
}

int main()
{
    char *str[] = { "Bharti", "Bharat", "Akas" };
    int a = PalindromeLengthPuzzle( str , sizeof( str ) / sizeof( *str ) );

    return 0;
}

and

#include<stdio.h>
#include<string.h>

int PalindromeLengthPuzzle( char* input1[] )
{
   // ...
}

int main()
{
    char *str[] = { "Bharti", "Bharat", "Akas", NULL };
    int a = PalindromeLengthPuzzle( str );

    return 0;
}

Here is a working example with sentinel

#include <stdio.h>

void PalindromeLengthPuzzle( char* input1[] )
{
    while ( *input1 ) puts( *input1++ );
}

int main(void) 
{
    char *str[] = { "Bharti", "Bharat", "Akas", NULL };

    PalindromeLengthPuzzle( str );

    return 0;
}

The output is

Bharti
Bharat
Akas

edited Apr 17 '15 at 10:03

answered Apr 17 '15 at 09:39

Vlad from Moscow

301,070
26
186
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Will this be permissible in my code `while(input1[i]!=NULL) { some logic; i++ ;}` ?? – G.S Abhaypal Apr 17 '15 at 09:52
@G.S Abhaypal Yes, you can check whether the next value is the sentinel.:) – Vlad from Moscow Apr 17 '15 at 09:53
This is what i got `BhartiBharatAkasÀÁo·àÃo·p°o·d°o·d°o·` , :/ i guess its going in infinite loop , and adding garbage values after actual values. – G.S Abhaypal Apr 17 '15 at 09:55
@G.S Abhaypal You have to include the last initializer equal to NULL as it is shown in my example. Wait a minute I will provide a working program. – Vlad from Moscow Apr 17 '15 at 09:56
i did this , `char *mystr[]={input1,NULL};` – G.S Abhaypal Apr 17 '15 at 09:59
Sorry sorry , actually i was looping through input1 , and i am appending sentinel value in mystr. – G.S Abhaypal Apr 17 '15 at 10:01
@G.S Abhaypal See my updated post where there is shown a working example. – Vlad from Moscow Apr 17 '15 at 10:04
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/75490/discussion-between-g-s-abhaypal-and-vlad-from-moscow). – G.S Abhaypal Apr 17 '15 at 10:04
Thanks for the update , but input is not in my hand. It is dynamic and i have to handle it completely in my function only. So i did following. `char *mystr[]={input1,NULL};` But while iterating , its showing garbage. – G.S Abhaypal Apr 17 '15 at 10:08

String Array Count

2 Answers2