2D array transpose matrix in C

Question

#include <stdio.h>

void read_array( int row, int col, int a[row][col]);
void fill_arr(int row, int col,int b[row][col], int a[row][col]);
void print_arr(int row, int col, int a[row][col]);

int main(void){
    int r1,c1;
    printf("Enter number of rows>");
    scanf("%d", &r1);
    printf("Enter number of columns>");
    scanf("%d", &c1);
    int arr[r1][c1];
    read_array(r1,c1,arr);
    int arr2[c1][r1];
    fill_arr(c1,r1,arr2,arr);
    print_arr(c1,r1,arr2);
}

void read_array( int row, int col, int a[row][col]){
    int i,j;
    printf("Enter values for %d rows with each row having %d numbers> ", row, col);
    for(i=0; i<row; i++){
        for(j=0; j<col; j++){
            scanf("%d", &a[i][j]);
        }
    }
}
void fill_arr(int row, int col,int b[row][col], int a[row][col]){
    int i,j;
    for(i=0; i<row;i++){
        for(j=0; j<col; j++){
            b[i][j] = a[j][i];
        }
    }
}
void print_arr(int row, int col, int a[row][col]){
    int i,j;
    printf("Transpose: \n");
    for(i=0; i<row; i++){
        for(j=0; j<col; j++){
            printf("%d ", a[i][j]);
        }
        printf("\n");
    }
}
/*Example for a 3x4 matrix with 1-12 as input:
    Expected output:
    1 5 9
    2 6 10
    3 7 11
    4 8 12

    Actual output:
    1 4 7
    2 5 8
    3 6 9
    4 7 10
/*

I'm trying to make a program to make a transpose matrix of a given matrix. Here, the last value of a column is being repeated for some reason. How can I fix this? (I'm aware there are other working codes for transpose matrix on stackoverflow. I need to find the problem in THIS code).

Answer 1

I believe you are mixing up c1 and r1 in the call to fill_array() .

Also, that function should be called transpose_array() or copy_transposed() . fill suggests you're filling with some fixed value or with zeros.

Answer 2

Hope this is useful.

void fill_arr(int row, int col,int b[col][row], int a[row][col]){
      int i,j;
      for(i=0; i<row;i++){
      for(j=0; j<col; j++){
        b[j][i] = a[i][j];
      }
    }
  }
void print_arr(int row, int col, int a[row][col]){
     int i,j;
     printf("Transpose: \n");
     for(i=0; i<row; i++){
      for(j=0; j<col; j++){
        printf("%d ", a[i][j]);
     }
      printf("\n");
}
}

int main(void){
int r1,c1;
printf("Enter number of rows>");
scanf("%d", &r1);
printf("Enter number of columns>");
scanf("%d", &c1);
int arr[r1][c1];
read_array(r1,c1,arr);
int arr2[c1][r1];
fill_arr(r1,c1,arr2,arr);
print_arr(c1,r1,arr2);

}