Convert two dimensional array to a one dimension by using pointer in C language

Question

I wanted to convert two dimensional array to a one dimension (array linearization ) by using a pointer and setting it to a particular character. Here is the code:

#define COLS 20
#define ROWS 10

void convert(void)
{

    char record[ROWS][COLS] = { 0 };

    char *pRecord = record;

    int i = 0;

    for (i = 0; i < (ROWS*COLS); i++)
    {
        *(pRecord++) = ' ';

    }

}

However, I am getting a compiler error in initializing the pointer to char array. I 'vd edited the code i.e it will be *pRecord, previously it was only pRecord. Need some help in understanding the error and if possible some suggestions to fix it.

You are trying to set a char pointer to a char. Try: char* pRecord = record — mikeyq6
– mikeyq6, Commented Feb 16, 2016 at 17:25

user1683793 · Accepted Answer · 2016-02-16 17:29:10Z

2

May I suggest you define the pointer as a pointer? This compiles cleanly on my machine:

char *pRecord = &record[0][0];

answered Feb 16, 2016 at 17:29

user1683793

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2 Comments

mikeyq6 Over a year ago

That is exactly the same effect as saying char *pRecord = record; :)

2501 Over a year ago

@mikeyq6 You should get a type warning for that. Luckily char* can alias that, but other types can't.

jxh · Accepted Answer · 2016-02-16 17:46:09Z

1

Your loop is implementing the equivalent of memset(record, ' ', sizeof(record)). A manual implementation would roughly look like:

char *pRecord = (void *)record;
size_t len = sizeof(record);
while (len--) *pRecord++ = ' ';

answered Feb 16, 2016 at 17:46

jxh

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Comments

Community · Accepted Answer · 2017-05-23 11:50:35Z

1

If you want to Convert two dimensional array to a one dimension, check this idea:

#include<stdio.h>
#define COLS 20
#define ROWS 10

void convert(void)
{
   int i,j;
   char  *pRecord ;
   char newArray [COLS * ROWS];
   pRecord  = newArray;
   char record[ROWS][COLS] = { 0 };

    for ( i = 0 ; i <  ROWS ; i++)
      for ( j = 0; j < COLS ; j++){
        *pRecord = record[i][j]; 


      }

}

Maybe this post will serve How do pointer to pointers work in C?

edited May 23, 2017 at 11:50

CommunityBot

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answered Feb 16, 2016 at 18:25

pazthor

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Comments

Mad Physicist · Accepted Answer · 2016-02-16 18:05:14Z

0

char (*pRecord)[COLS];
pRecord = record;

Though, in the case of array, that will turn out in this way.

pRecord == *pRecord

edited Feb 16, 2016 at 18:05

Mad Physicist

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answered Feb 16, 2016 at 17:59

nariuji

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