I am trying to type in a matrix and then print it, using functions.
The program crashes when it gets to the read_mat function. What am I getting wrong?
#include <stdio.h>
#include <stdlib.h>
int** insert_mat(int **mat, int r, int c);
int** read_mat(int** mat, int r, int c)
{
mat = (int**)calloc(r,sizeof(int*));
for (int i=0; i<r; i++)
{
mat[i]=(int*)calloc(c,sizeof(int));
}
insert_mat(mat, r, c);
return mat;
}
int** insert_mat(int **mat, int r, int c)
{
for (int i=0; i<r; i++)
{
for(int j=0; j<c; j++)
{
printf("\nmat[%d][%d] = ",i , j);
scanf("%d", &mat[i][j]);
}
}
return mat;
}
void print_mat(int **mat, int r, int c)
{
printf("\n");
for (int i=0; i<r; i++)
{
for(int j=0; j<c; j++)
{
printf("%d ",mat[i][j]);
}
printf("\n");
}
}
int main()
{
int **mat;
int r1 =2;
int c1 = 2;
read_mat(mat, r1, c1);
print_mat(mat, r1, c1);
return 0;
}
I also tried printing elements of mat in main (ex: printf("%d", mat[0][0]);) and it is also not working. So maybe the error is when I insert the elements? But I am not sure what I do wrong.
Related
I am trying to create a program to find the transpose of a matrix my dynamic memory allocation. However, while entering the elements of the matrix I can't input more than one element, its only taking the a[0][0] as the input and the program is ending after that.
#include <stdio.h>
#include <stdlib.h>
void createMatrix(int **, int, int);
void inputElements(int **, int, int);
void transpose(int **, int **, int, int);
void display(int **, int, int);
void main()
{
int **matrix, **trans, rows, cols;
printf("\nEnter number of rows in the matrix: ");
scanf("%d", &rows);
printf("\nEnter number of columns in the matrix: ");
scanf("%d", &cols);
createMatrix(matrix, rows, cols);
createMatrix(trans, cols, rows);
inputElements(matrix, rows, cols);
transpose(matrix, trans, rows, cols);
printf("\nMATRIX:\n");
display(matrix, rows, cols);
printf("\nTRANSPOSE OF THE MATRIX:\n");
display(trans, rows, cols);
}
void createMatrix(int **a, int r, int c) //for allocating memory for the matrix
{
int i, j;
a = (int **)malloc(sizeof(int *) * r);
for(i = 0; i < r; i++)
a[i] = (int *)malloc(sizeof(int) * c);
}
void inputElements(int **a, int r, int c) //for entering matrix elements
{
int i, j, t;
for(i = 0; i < r; i++)
{
for(j = 0; j < c; j++)
{
printf("\nEnter matrix element[%d][%d]: ", i + 1, j + 1);
fflush(stdin);
getchar();
scanf("%d", &(a[i][j]));
}
}
}
void transpose(int **a, int **t, int r, int c) //for finding out the transpose of the matrix
{
int i, j;
for (i = 0; i < c; i++)
{
for (j = 0; j < r; j++)
t[i][j] = a[j][i];
}
}
void display(int **a, int r, int c) //for displaying the matrix
{
int i, j;
for (i = 0; i < r; i++)
{
printf("\n");
for (j = 0; j < c; j++)
printf("\t%d", a[i][j]);
}
}
There are many posts about scanf in loops I've seen, but I wasn't able to connect my issue with any of them.
i am learning pointers and i write these code to add two martix via function, it compile well and give correct answer for 2x2 matrix but for more than two row and col it fails when i try it with 3x3 matrix [0][0] element for the first matrix it automaticaly become 6 and [1][0] it became 9 every time, i can't figure out why this happen
#include <stdio.h>
//-----------------Function------------------
void add(int (*p1)[10], int (*p2)[10], int (*p3)[10], int r, int c);
void get(int (*p1)[10], int r, int c);
void print(int (*p1)[10], int r, int c);
//---------------Main Program----------------
int main()
{
//declartion
int i, j, r, c;
printf("\n\tenter the row and column of matrix\n\t");
scanf("%d %d", &r, &c);
int m1[r][c], m2[r][c], m3[r][c];
printf("\n\tenter the element of first matrix\n\t");
get(m1, r, c);
print(m1, r, c);
printf("\n\tenter the element of second matrix\n\t");
get(m2, r, c);
print(m2, r, c);
add(m1, m2, m3, r, c);
printf("\n");
print(m3, r, c);
return(0);
}
//-------------Define Function---------------
//get()
void get(int (*p1)[10], int r, int c)
{
int i, j;
for(i = 0; i < r; i++)
{
printf("\n\t");
for(j = 0; j < c; j++)
{
scanf("%d", (*(p1+i)+j));
}
}
}
//--------------------X----------------------
//add()
void add(int (*p1)[10], int (*p2)[10], int (*p3)[10], int r, int c)
{
int i, j;
for(i = 0; i < r; i++)
{
for(j = 0; j < c; j++)
{
//printf("\n%d %d = %d & %d", i, j, *(*(p1+i)+j), *(*(p2+i)+j));
*(*(p3+i)+j) = *(*(p1+i)+j) + *(*(p2+i)+j);
}
}
}
//--------------------X----------------------
//print()
void print(int (*p1)[10], int r, int c)
{
int i, j;
for(i = 0; i < r; i++)
{
printf("\n");
for (j = 0; j < c; j++)
{
printf("\t%d", *(*(p1+i)+j));
}
}
}
//--------------------X----------------------
Drop the array pointer notation and the fixed size. Use variable-length arrays based on the parameters.
Remove useless comments like // get ... void get...
Don't use unreadable de-referncing with *(arr+i) when you could be writing readable arr[i].
Print new line after each row, not before each row.
Here's a cleaned up program which compiles. I haven't tested it.
#include <stdio.h>
void add (int r, int c, int p1[r][c], int p2[r][c], int p3[r][c]);
void get (int r, int c, int p1[r][c]);
void print (int r, int c, int p1[r][c]);
int main (void)
{
int i, j, r, c;
printf("\n\tenter the row and column of matrix\n\t");
scanf("%d %d", &r, &c);
int m1[r][c], m2[r][c], m3[r][c];
printf("\n\tenter the element of first matrix\n\t");
get(r, c, m1);
print(r, c, m1);
printf("\n\tenter the element of second matrix\n\t");
get(r, c, m2);
print(r, c, m2);
add(r, c, m1, m2, m3);
printf("\n");
print(r, c, m3);
return(0);
}
void get (int r, int c, int p1[r][c])
{
for(int i = 0; i < r; i++)
{
for(int j = 0; j < c; j++)
{
scanf("%d", &p1[i][j]);
}
}
}
void add (int r, int c, int p1[r][c], int p2[r][c], int p3[r][c])
{
for(int i = 0; i < r; i++)
{
for(int j = 0; j < c; j++)
{
p3[i][j] = p1[i][j] + p2[i][j];
}
}
}
void print (int r, int c, int p1[r][c])
{
for(int i = 0; i < r; i++)
{
for (int j = 0; j < c; j++)
{
printf("\t%d", p1[i][j]);
}
printf("\n");
}
}
i successfully run it on codeblocks, but my clion doesnt display anything when i run it.
i usually use clion, so im very furious about this. (dont want to be obligated to use codeblocks)
please help a poor lost soul.
this is the code.
dont have a lot more to say, but still stackoverflow wants me to write more, so here i am.
#include <stdio.h>
#include <stdlib.h>
int **malloc2dR(int r,int c);
int **MATinit(int r, int c);
void MATstampa(int **m, int r, int c);
void change(int **M, int r, int c);
int main() {
int r=3,c=4;
int **M=MATinit(r,c);
MATstampa(M,r,c);
change(M,r,c);
MATstampa(M,r,c);
return 0;
}
int **malloc2dR(int r, int c){
int **m;
int i;
m=malloc(r*sizeof (int *));
for(i=0;i<r;i++)
m[i]=malloc(c*sizeof (int));
return m;
}
int **MATinit(int r, int c){
int **M=malloc2dR(r,c);
int i,j;
printf("scrivere in input i valori della matrice %dx%d\n",r,c);
for(i=0;i<r;i++)
for(j=0;j<c;j++)
scanf("%d",&M[i][j]);
return M;
}
void MATstampa(int **m, int r, int c){
int i,j;
for(i=0;i<r;i++) {
for (j = 0; j < c; j++)
printf("%d ", m[i][j]);
printf("\n");
}
printf("\n");
}
void change(int **M, int r, int c) {
int i, j;
int ii, jj;
int **Mfake=malloc2dR(r,c);
for(i=0;i<r;i++)
for(j=0;j<c;j++)
Mfake[i][j]=M[i][j];
for (i = 0; i < r; i++)
for (j = 0; j < c; j++)
if (M[i][j] % 2 == 1) {
for (ii = 0; ii < r; ii++)
Mfake[ii][j] = 1;
for (jj = 0; jj < c; jj++)
Mfake[i][jj] = 1;
}
for(i=0;i<r;i++)
for(j=0;j<c;j++)
M[i][j]=Mfake[i][j];
}
I feel like I've attempted every combination I know of to get this to work and can't figure it out. How can I scanf() into an int** passed as a pointer to a function? I tried searching but couldn't find this, if it's a duplicate please let me know and I'll delete. It begins to run and after entering a few values it segfaults.
Here's my code, I think it's messing up on the scanf() line of the setMatrix() function:
#include <stdio.h>
#include <stdlib.h>
// create zero initialized matrix
int** callocMatrix(int rmax, int colmax) {
int **mat = calloc(rmax, sizeof(int*));
for(int i = 0; i < rmax; i++) mat[i] = calloc(colmax, sizeof(int));
return mat;
}
// fill matrix
void setMatrix(int ***mat, int r, int c){
printf("Insert the elements of your matrix:\n");
for (int i = 0; i < r; i++) {
for (int j = 0; j < c; j++) {
printf("Insert element [%d][%d]: ", i, j);
scanf("%d", mat[i][j]); // problem here??
printf("matrix[%d][%d]: %d\n", i, j, (*mat)[i][j]);
}
}
return;
}
// print matrix
void printMatrix(int ***mat, int r, int c){
for (int i=0; i<r;i++){
for (int j=0; j<c;j++) {
printf("%d ", (*mat)[i][j]);
}
printf("\n");
}
}
int main(int argc, char *argv[]) {
int r = 3, c = 3;
int **mat = callocMatrix(r, c);
setMatrix(&mat, r, c);
printMatrix(&mat, r, c);
}
There is no need to use triple pointer ***. Passing two-dimensional array will work as is. Here is the code:
#include <stdio.h>
#include <stdlib.h>
// create zero initialized matrix
int** callocMatrix(int rmax, int colmax) {
int **mat = calloc(rmax, sizeof(int*));
for(int i = 0; i < rmax; i++) mat[i] = calloc(colmax, sizeof(int));
return mat;
}
// fill matrix
void setMatrix(int **mat, int r, int c){
printf("Insert the elements of your matrix:\n");
for (int i = 0; i < r; i++) {
for (int j = 0; j < c; j++) {
printf("Insert element [%d][%d]: ", i, j);
scanf("%d", &mat[i][j]); // no problem here
printf("matrix[%d][%d]: %d\n", i, j, mat[i][j]);
}
}
}
// print matrix
void printMatrix(int **mat, int r, int c){
for (int i=0; i<r;i++){
for (int j=0; j<c;j++) {
printf("%d ", mat[i][j]);
}
printf("\n");
}
}
int main(int argc, char *argv[]) {
int r = 3, c = 3;
int **mat = callocMatrix(r, c);
setMatrix(mat, r, c);
printMatrix(mat, r, c);
}
Should be:
scanf("%d", &(*mat)[i][j]);
You're passing a pointer to you matrix object, so you need to dereference it (with *) just as you do with printf. scanf then needs the address of the element to write into, so you need the &
I have an issue passing a matrix to a function in C. There is the function I want to create:
void ins (int *matrix, int row, int column);
but I noticed that in contrast to the vectors, matrix give me an error. How can I pass my matrix to a function so?
EDIT --> there is the code:
// Matrix
#include <stdio.h>
#define SIZE 100
void ins (int *matrix, int row, int column);
void print (int *matrix, int row, int column);
int main ()
{
int mat[SIZE][SIZE];
int row, col;
printf("Input rows: ");
scanf ("%d", &row);
printf("Input columns: ");
scanf ("%d", &col);
printf ("Input data: \n");
ins(mat, row, col);
printf ("You entered: ");
print(mat, row, col);
return 0;
}
void ins (int *matrix, int row, int column);
{
int i, j;
for (i = 0; i < row; i++)
{
for (j = 0; j < column; j++)
{
printf ("Row %d column %d: ", i+1, j+1);
scanf ("%d", &matrix[i][j]);
}
}
}
void print (int *matrix, int row, int column)
{
int i;
int j;
for(i=0; i<row; i++)
{
for(j=0; j<column; j++)
{
printf("%d ", matrix[i][j]);
}
printf("\n");
}
}
You need to pass a pointer with as much levels of indirection (*) as the number of dimensions of your matrix.
For example, if your matrix is 2D (e.g. 10 by 100), then:
void ins (int **matrix, int row, int column);
If you have a fixed dimension (e.g. 100), you can also do:
void ins (int (*matrix)[100], int row, int column);
or in your case:
void ins (int (*matrix)[SIZE], int row, int column);
If both your dimensions are fixed:
void ins (int matrix[10][100], int row, int column);
or in your case:
void ins (int matrix[SIZE][SIZE], int row, int column);
If you have a modern C compiler you can do the following for 2D matrices of any sizes
void ins (size_t rows, size_t columns, int matrix[rows][columns]);
Important is that the sizes come before the matrix, such that they are known, there.
Inside your function you then can access the elements easily as matrix[i][j] and the compiler is doing all the index calculations for you.
it would also possible to leave the first dimension empty, the same as (*matrix):
void ins (int matrix[][100], int row, int column);
Much better way to use malloc function and create dynamically allocated array and do whatever you want to do using 2d array:
#include <stdio.h>
#include <stdlib.h>
#include <stdio.h>
void fun(int **arr,int m,int n)
{
int i, j;
for (i = 0; i < m; i++)
{
for (j = 0; j < n; j++)
{
scanf("%d", &arr[i][j]);
}
}
}
int main()
{
int i,j,m,n;
printf("enter order of matrix(m*n)");
scanf("%d*%d",&m,&n);
int **a=(int **)malloc(m*sizeof(int));
for(i=0;i<n;i++)
a[i]=(int *)malloc(n*sizeof(int));
fun(a,m,n);
for (i = 0; i < m; i++)
{
for (j = 0; j < n; j++)
{
printf("%d ", a[i][j]);
}
printf("\n");
}
return 0;
}
output:
#include <stdio.h>
#include <stdlib.h>
#include <stdio.h>
void fun(int **arr,int m,int n)
{
int i, j;
for (i = 0; i < m; i++)
{
for (j = 0; j < n; j++)
{
scanf("%d", &arr[i][j]);
}
}
}
int main()
{
int i,j,m,n;
printf("enter order of matrix(m*n)");
scanf("%d*%d",&m,&n);
int **a=(int **)malloc(m*sizeof(int));
for(i=0;i<n;i++)
a[i]=(int *)malloc(n*sizeof(int));
fun(a,m,n);
for (i = 0; i < m; i++)
{
for (j = 0; j < n; j++)
{
printf("%d ", a[i][j]);
}
printf("\n");
}
return 0;
}
You can try this as well:
void inputmat(int r,int c,int arr[r * sizeof(int)][c * sizeof(int)])