i have some bidimensional arrays like:
int shape1[3][5] = {1,0,0,
1,0,0,
1,0,0,
1,0,0,
...
|
I have the following function
void initBoard(int * board[BOARD_ROWS][BOARD_COLS]){
int z = 0;
for( z = 0; z<10; z+=1){
int l;
for( ...
|
i need a ptr to a static 2-dimensional array. How is this done?
static uint8_t l_matrix[10][20];
void test(){
uint8_t **matrix_ptr = l_matrix; //wrong idea
}
i dont get it, but all kinds ... |
I am doing lots of matrix arithmetic and would like to take advantage of C99's restrict pointer qualifier.
I'd like to setup my matrices as pointers to pointers to allow for easy ... |
I have the following homework question:
Consider the following declarations and answer the question.
char strarr1[10][32];
char *strarr2[10];
Are strarr1[3][4] and strarr2[3][4] both legal references?
I tried compiling the code with gcc to test it. I ... |
How do I pass the m matrix to foo()? if I am not allowed to change the code or the prototype of foo()?
void foo(float **pm)
{
int i,j;
...
|
I want to scan a 2D array with the help of pointers and have written this code, could you tell me why the compiler gives errors? I know how to use ... |
|
Addresses of 1d arrays are actually taken as
a[i]=*(a+i);
Are the addresses of 2d arrays calculated as
a[i][j]=**(a+i+j);
|
I took a hiatus from C and am just getting back into it again.
If I want to create a 2D array of doubles, I can do it two ways:
double** m_array = ...
|
Just trying to really get my head round Arrays and Pointers in C and the differences between them and am having some trouble with 2d arrays.
For the normal 1D array this ... |
If the following is possible:
MyFunction(int *array, int size)
{
for(int i=0 ; i<size ; i++)
{
printf(“%d”, array[i]);
...
|
Here is a code which print the address of the first element of an 2D array followed by an addition of 1. Though all 4 base addresses are same but their ... |
I am generating contiguous 2d arrays using the method posted on here by Shawn Chin.[1][2] It works very well.
Briefly from his post:
char** allocate2Dchar(int count_x, int count_y) {
int i;
...
|
For my program I need to pass a 2D array of pointers to a function in a separate file. I've written a similarly-syntaxed file below:
#include <stdlib.h>
#include <stdio.h>
typedef struct {
int ...
|
I am trying to tokenize a line and put it into a two dimensional array so far I have come up with this but I feel I am far off:
/**
* ...
|
Hey All, I am a pointer newbie and in the following code, I am trying to store the values of a 2 D array in a structure and then print them. ... |
I imagine we all agree that it is considered idiomatic C to access a true multidimensional array by dereferencing a (possibly offset) pointer to its first element in a one-dimensional fashion, ... |
int a[3][4] = {
1,2,3,4,
5,6,7,8,
...
|
I'm experimenting with the concept of pointer to multi-dimension array in C. Suppose I want to process a multi-dimensional array via a function. The code kinda looks like this:
#include <stdio.h>
void proc_arr(int ...
|
I have a 2d array like this...
char a[][20]={"Hi","Hello","Bye","Good Morning"};
Now I need a char pointer to refer this array , modify one of the string in the array through pointer and print ... |
I know how to work pointers with a unidimensional array,(the identifier of the array points to its first element)..., but i would like to know how can i work the same ... |
If I have this reference variable:
float* image
How can I get the length of this image in C? The length = (width * height) but how can I get this value?
|
Hello every one I want to ask how to fill 2D array using pointer. I know how to fill 1D array
like
*(i+array) = 0;
but if i have array like this
int ...
|
Let's say I have 2 2-dimensional arrays:
int a1[][2] = { {1,2}, {3,4}, {5,6} };
int a2[][2] = { {7,8}, {9,0}, {1,1} };
and a pointer:
int *a;
The pointer will point to one of the ... |
The basic problem is that your array is 10 elements where each element is an array of 10 int. Therefore, the name "array" is the address of element 0. Elemet 0 is an array of 10 int. Therefore, the name "array" must be passed to a pointer to an array of 10 int. That is, a (*pp1)[10]. Calling the address of ... |
T[0] is a pointer since this is a 2-D array . If you want to you could substitute &T[0][0] (see the Arrays Revealed that Don had recommended). I was commenting before that you have the calculation i+j*MAXROW, but that's not how arrays are laid out in memory, where the column is offset into it's particular row. |
PeterOut int Func(float **fppArg); > and I have a variable defined thus. > float faa2DArray[3][3]; > How would I pass faa2DArray to Func()? You can't, at least not directly. You can write: float *tmp[] = { faa2DArray[0], faa2DArray[1], faa2DArray[2] }; Func(tmp); or even: Func((float *[]){faa2DArray[0], faa2DArray[1], faa2DArray[2]}); if you don't mind straying ... |
Hello, is there something neat in the c++ standard library that can help me set all elements of a two-dimensional array of pointers to NULL? Like fill_n(), maybe? Right now, I'm using two for loops (one nested) and wanted to know what alternatives there are. My compiler ships with a preliminary TR1-implementation. Another thing I need to do is to call ... |
Dear All, there have been several threads on multidimensional arrays and pointers to arrays, there is still something I could not fully understand. (My point here I have raised already, but stayed unanswered) Let's have an array. float A[256]; And you would like to consider this as 32x8 matrix. You can of course do A[32*i+j] for the (i,j)-th element, but it ... |
On Apr 26, 12:26 pm, "lovecreatesbea...@gmail.com" For example: int *mtxrot1d(int *p, int n); int a2[N][N]; int a3[N][N][N]; > mtxrot1d((int*)a2); mtxrot1d((int*)a3); > Thank you for your time. Of ... |
Hi all, I'm not a very experienced C programmer and probably miss something very basic, so please forgive me. I modified a function that tests whether a point lies within a polygon (from the comp.graphics.algorithms FAQ at http://www.cgafaq.info/wiki/Point_in_polygon). Instead of two one-dimensional arrays I wanted to use one two- dimensional array as argument. But I can't figure out how to call ... |
Hello everyone, merry christmas! I have some questions about the following program: arrtest.c ------------ #include int main(int agc, char *argv[]) { int array2d[2][2] = { {1,2} , {3,4} }; int (* arrp)[2] = array2d; printf("&array2d = %p\tarray2d = %p\t*array2d = %p\n", &array2d, array2d, *array2d); printf("&arrp = %p\tarp = %p\t*arrp = %p\t**arp = %d\n", &arrp, arrp, *arrp, **arrp); return 0; } ... |
On thing I have found out so far. int array[ ][ ] is equivalent to int (*ptr)[] But how do I perform the pointer arithmetic and allocate memory at the same time? for(/*for conditions*/) { (*prt ) = malloc(sizeof( int[] )) for(/*for conditions*/) (*prt + /*increment value*/)[/*increment value*/] = /*some value*/ I do not have a clue.... |
i have written this program of entering 2-d array through pointers.this shows number of errors.please help me out. #include #include void aread(int*[],int*,int*); void awrite(int*[],int*,int*); void addarray(int*[],int*[],int*[],int*,int*); void aread(int*a[],int *m,int *n) { int i,j; printf("Enter array size = "); scanf("%d%d",*m,*n); for(i=0;i<*m;i++) { *(a+i)=(int*)malloc(sizeof(m+1)); for(j=0;j |
|
how i can put 2d array to a pointer? In the below program i am giving a first value to output_bit and then start to a loop and putting the new values to an another array as called newdata[l][k]. But as i understand from this loop the last value of the 2d array u[l][k] is not put to newdata[l][k]. Because of ... |
Hi, I'm trying to use the HDF library to read a few HDF files that I need to process. The data in each file varies in rows, but the columns remain constant. Because of that, I had dynamically allocated a set of pointer to pointers as my multi-dimensional arrays. Here is my code (i have omitted checking calloc's return value to ... |
Mark wrote:[color=blue] > put most simply, what is the c++ equivalent to this java code? > > int map[][]; > map = new int[16][16]; > map[5][5] = 3; > System.out.println(map[5][5]); > > thanks in advance.[/color] You can use vector to simulate this dynamically. #include #include using namspace std; ..... vector > MyMap(16, vector(16)); MyMap[5][5] = 3; cout << MyMap[5][5] ... |
//implement 2D array& pointer,crash in execute time not complete insert elements #include #include #include void main () { int i,j,n,r,c; int **p; printf("enter the row and column of matrix:\n"); scanf("%d %d",&r,&c); p=(int**)malloc(r*sizeof(int)); p=(int**)malloc(c*sizeof(int)); printf("enter the elements\n"); for(i=0;i |
To answer "Tater's" question, I am using pointer arithmetic becuase i want to take certain columns out of an array and pass them to atol(). In my case the 5th column in each row starts a 4 byte number. I want to perform an atol( mat[3][4] ) for example to take bytes 4 thru 8 from row 3 and convert to ... |
|
So if we have int a[2][2], then when you pass it to a function you get, as you say, int (*p)[2]. That means that p+1 advances it forward by the amount pointed to. p pointed to array-of-two-ints, so +1 moves forward by one set-of-two-ints, which means it points to the second row of your original array. Then you dereference to get ... |
#include int main(void) { int s[5][2] = { { 1234, 56 }, { 1212, 33 }, { 1434, 80 }, { 1312, 78 } } ; int ( *p )[2] ; int i, j, *pint ; for ( i = 0 ; i <= 3 ; i++ ) { p = &s[i] ; pint = p ; printf ( "\n" ... |
|
Hello, Yes its homework but I feel im very close. I am getting junk values for "subtot" in my last for statement. Everything else seems to be working well. I've searched the board and can't seem to get my last bit of code working. Any help guys and gals? TIA Code: * rain.c finds yearly totals, yealy average, and monthly average ... |
|
I dont understand your second sentence here... is it related to the first? Anyways, the purpose of "stringsize" as recommended by zacs7 is simply to use it to declare a constant "maximum" size of each string (or each char* in the array). You must allocate some memory to the pointer before using it, so its good to define some constant value ... |
Code: #include "matrix.h" matrix create_empty(int rdim, int cdim) { matrix* new_matrix; new_matrix = malloc(sizeof(matrix)); new_matrix -> rowdim = rdim; new_matrix -> coldim = cdim; new_matrix -> element = malloc((rdim*cdim) * sizeof(double)); return *new_matrix; } matrix create_initval(int rdim, int cdim, double* values) { int i, j; matrix* new_matrix; new_matrix = malloc(sizeof(matrix)); new_matrix -> rowdim = rdim; new_matrix -> coldim = cdim; new_matrix ... |
With a regular 2D array, (not a pointer to an array), couldn't you use a regular pointer? Would you need a pointer to a pointer before the array was degraded to a double pointer? After the array has degraded, I'd think you'd want a pointer to a pointer for a 2D array. |
|
Hi, I'm trying to write a simple application to initialise a 2d array, and later manipulate the values by performing some maths on the values. I started out trying to use the declaration: double array[5][5], which was working until i needed to pass the array into functions. I then thought i would need to use a double pointer: double **array for ... |
Code: /************************************************************************************ print_matrix(): This will print the contents of the matrix M which has r rows and c columns. The matrix will be printed one row per line. Each row will be printed between pipe characters('|'). Each element of the vector will have a field width of 8 and each element will be left aligned within that field. ************************************************************************************/ void print_matrix(int ... |
|
|
#include int add(int (*a1)[][3], int (*a2)[][3], int (*a3)[][3]){ int i,j; for(i=0;i<3;i++){ for(j=0;j<3;j++){ a3[i][j]=a1[i][j]+a2[i][j]; } } return 0; } int main (){ int size1,size2; int i,j; printf("enter the size of a square matrix:"); scanf("%d",&size1); int a1[size1][size1]; for(i=0;i |
|
|
#include #include void print(int** array) { int i, j; for(i=0; i<4; i++) { for(j=0; j<4; j++) printf("%d\t",array[i][j]); printf("\n"); } } int main() { int i,j; int array[4][4]; for(i=0; i<4; i++) for(j=0; j<4; j++) array[i][j] = 123; int** ptr_array; int* outer_ptr_array[4]; for (i = 0; i < 4; ++i) outer_ptr_array[i] = array[i]; ptr_array = outer_ptr_array; print(ptr_array); } |
#include float avg(int **array, int row, int col) { int i,j, count=0; float calculation = 0, average; for(i=0; i |
#include #include #define L1 3 #define C1 2 #define L2 4 #define C2 3 void escreve1(int mat[][C1],int lin, int col); void escreve2(int mat[][C2],int lin, int col); void main() { int mat1[L1][C1]={{1,2},{3,4},{5,6}}; int mat2[L2][C2]={{1,2,3},{4,5,6},{7,8,9},{10,11,12}}; printf("\nMatriz mat1:\n"); escreve1(mat1, L1, C1); printf("\nMatriz mat2:\n"); escreve2(mat2, L2, C2); } void escreve1(int mat[][C1] , int lin, int col) { int *z; for(z=mat[0];z |
|
Hi, all I am having a trouble with pointer and multi-dimensional array. I wrote the same thing but I see different output. below is the code Code: #include void printarray_1 (int (*ptr)[4]); void printarray_2 (int (*ptr)[4], int n); int main(void) { int multi[3][4] = { {1,2,3,4}, {5,6,7,8}, {9,10,11,12} }; /* ptr is a pointer to an array of 4 ints. ... |
Code: #include "stdafx.h" #include "math.h" int main(int argc, char* argv) { int i,j; int **matrix = NULL; int numRows; int numCol; printf( "Enter the number of rows: "); scanf( " %d", &numRows); printf( "Enter the number of columns: "); scanf( " %d", &numCol); matrix = malloc(numRows * sizeof(*matrix)); for (i = 0; i < numRows; i++) { matrix[i] = malloc(numCol * ... |
int main() { char gameGrid[8][8]; /* I just want to understand how to pass the grid as reference and fill in using pointers */ initialGrid( gameGrid, 8, 8); /* I will be remove hard coding later*/ } void initialGrid(char *grid, int colsize, rowsize) { int i,j for (i=0; i |
Code: #include void printm( const int *pnum, int x, int y ) { for ( int j=0; j |
|
Here is what I want to do: 1. I have two arrays - one with new data and one with old. I effectively want to swap the pointer such that the pointer to the new data points at the old and the new data storage is deleted (i.e. no leaks). 2. I seem to be failing at the syntax stage. Tying ... |
#include #define LEN 10 void f1 ( int a[LEN][LEN] ) { a[0][0] = 0; } void f2 ( int a[][LEN] ) { a[0][0] = 0; } void f3 ( int (*a)[LEN] ) { a[0][0] = 0; } void f4 ( int (*a)[LEN][LEN] ) { // watch the extra level of indirection needed (*a)[0][0] = 0; } int main ( void ) ... |
hey...i need to create an array of locations on the hard drive. at least i think thats how i want to do it as i've tried learning linked lists before and they just dont click. idky, but i dont get it. lol but basically i have a program that lets you search non-executable files for a specified string / strings. after ... |
|
I am not entirely clear on how to do pointers to multidimensional arrays. It seems that if p is a pointer to the first element of the multidimensional array then you cannot properly use the "p[i][j]" notation (my compiler returns an error, something along the lines of "subscripted value is neither an array nor a pointer"). Instead, you have to do ... |
#include #include double matnorm1(double **A, int m, int n) { double norm=0.0; double temp; int x; int y; for (x=0; xnorm) norm=temp; } return(norm); } double matnorminf(double **A, int m, int n) { double norm=0.0; double temp; int x; int y; for (x=0; x |
|
#include #include int studentgrades [10][5]={0}; int a; /* Enter grades for a student */ int enter_grades(){ int j; printf ("Enter student number you want to enter grades for: "); scanf ("%d", &a); printf ("Enter grades for student number %d: ", a); for (j = 0; j<5; j++){ scanf ("%d ",((studentgrades+a)+j);} printf ("Thank you!"); } |
|
#include #include #include #include #include "Dictionary.h" int count=0; int main(){ dic dicptrs[20]; char k[20], v[20]; int insert; dicptrs[count]= CreateDictionary(); printf("Enter a name:"); scanf("%s", &k); printf("Enter a number:"); scanf("%s", &v); insert = InsertEntries(dicptrs[20],k,v); printf("%s and %s\n", dicptrs->keys, dicptrs->values); } /****************CreateDictionary******************************/ Dictionary* CreateDictionary(void){ /* Pre: True * Post: size of dictionary = 0 && count = 0 */ dic ... |
Code: #include #include int main ( ) { int arr[10][20]; // a 2D array int (*pa)[20]; // a pointer to a 2D array int **b; // a pointer to a pointer int cols; // simple point at the given array pa = arr; // you can also call malloc to initialise // this synthesises arr[30][20] // the major size ... |
#include void input(char **array) { FILE* user; char filename[FILENAME_MAX]; int x, y; printf("Please specify a filename:"); scanf("%s", filename); if ((user = fopen(filename, "r")) != NULL) { for(y=0; y++; y<20) { for(x=0; x++; x<20) { **array[x][y] = fgetc(user); } } } else { printf("error opening file\n"); } } int main() { char inputarray [20][20]; input(&inputarray[][20]); } |
hi i want to create a array of pointer to a 2-d array of int type?? specs are that each 2-d array can have different dimensions given by user dynamically...and how to access it.. By Now what i have done is int (*arr)[dim] = x //x is a 2d array but how to create array of pointer for it and with ... |
|
|
#include #define ROWS 2 #define COLS 2 int multi[ROWS][COLS]; int (*pmulti)[ROWS][COLS] = multi; int main(void) { int row, col; for (row = 0; row < ROWS; row++) { for (col = 0; col < COLS; col++) { scanf("%d", pmulti); ++pmulti; } } for (row = 0; row < ROWS; row++) { for (col = 0; col < COLS; col++) { ... |
Hi guys, I'm pretty much a C newbie, but I've dabbled in other languages over the years. For my current project I'm using mikroElektronica Pro C on a PIC microcontroller. I've got a 2-dimensional array defined like this: Code: const char FONTTABLE[96][5]= { {0x00,0x00,0x00,0x00,0x00}, {0x00,0x00,0x5f,0x00,0x00}, {0x00,0x07,0x00,0x07,0x00}, /** [90 rows snipped] **/ {0x00,0x41,0x36,0x08,0x00}, {0x10,0x08,0x08,0x10,0x08}, {0x78,0x46,0x41,0x46,0x78} }; I want to select a given ... |
well, I am studkup in one thing... i have an array[size1][size2] and i would like check the contents of array[0][size2] if it matches with something. i know i can do checking with array[0][1],array[0][2] and so on...but i am thinking to use pointer to follow it..how do i do it ? it is like char **tracer, array[size1][size2]; *tracer[]=array[0][size2]; while (**tracer) { //do ... |
|
|
The compiler calculates offsets when you use an array and since you allocated only a single dimensional array, when it tries to access the calculate offsets it is having problems (it is good that the program crashed else you would have nightmarish bugs). You need to first allocate an array of POINTERS, then allocate memory for each pointer (or you could ... |
At the risk of being flamed (and yes I did search), I was wondering how pointers to multidimensional arrays work. If you pass 3x3 integer array, for example, to a function, how would you access each element? Since the name of the array is the address, incrementing the address should give you access to each element of row zero. And incrementing ... |
Hai all, Is it possible to declare 2 dimensional arrays with pointers and allocate memory for them seperately? I tried doing short *img[512][512]; img = (short*)malloc(512*512 * sizeof(short)); but this wouldn't work.It works fine if i do short *image; image = (short*)malloc(size2 * sizeof(short)); I am reading a 2dimensional image into this.I would like to read them as two dimensional itself ... |
I have a function that fills a 2D array with verticies but i want the 2D array to be declared outside the function, where the size is unknown. so the function only manipulates the array. I don't know what parameter to pass in, or how to declare the function. Can someone have a read, and tell me the right (better) way ... |
No it's not universally true. The issue is that your first example is using the array as a 2-dimensional array, and the second is treating it as a one-dimensional array. The second is faster than the first (or, more accurately, guaranteed to be no slower) because the first form requires the compiler to work out offsets in terms of rows and ... |
>> whoknows = 0; is the same as setting the pointer to null You must allocate space for this char array. I would suggest simply defining it as char whoknows[64]={0}; >>array_PTR[i][j] = *whoknows ; This will not work. You are not copying the conents to the array element but setting the element to a pointer to a local variables memory address. ... |
|
#include #include void myfunction(int **array1, int **array2) { int i = 0, j = 0; for (i = 0; i < 4; ++i) { for (j = 0; j < 4; ++j) { fprintf(stdout, "ans->%d\n", array1[i][j]); fprintf(stdout, "ans->%d\n", array2[i][j]); } } } int main(int argc, char**argv) { int i = 0, j = 0; int **myarray1; int **myarray2; myarray1 ... |
#include #include const char FONTTABLE[6][5]= { {0x00,0x00,0x00,0x00,0x00}, {0x00,0x00,0x5f,0x00,0x00}, {0x00,0x07,0x00,0x07,0x00}, {0x00,0x41,0x36,0x08,0x00}, {0x10,0x08,0x08,0x10,0x08}, {0x78,0x46,0x41,0x46,0x78} }; int main(int argc, char**argv) { int i = 0, j = 0; for (i = 0; i < 6; ++i) { fprintf(stdout, "row[%d]\n", i); for (j = 0; j < 5; ++j) { fprintf(stdout, " 0x%x", FONTTABLE[i][j]); } fputs("\n", stdout); } exit(EXIT_SUCCESS); } |
|
If you need to dynamically allocate the multidimensional arrays, try: CODE #include #include #define DIM_ONE_SIZE 10#define DIM_TWO_SIZE 256int main(){ int i; //Allocate dimension one char** multiDimArray = calloc (DIM_ONE_SIZE, sizeof(char*)); //Allocate dimension two for(i=0; i |