How do I rotate a matrix? C [closed] - c

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I want a matrix to rotate right. It's working for a square matrix, but i should also work for non square matrix.
I tried rotating it, but i couldn't think of a way to get it to work for non square matrix.
#include <stdio.h>
#define x 7
#define y 7
int build() {
int i = 0, k = 0;
int matrix[x][y];
for (i = 0; i < x; ++i) {
for (k = 0; k < y; ++k) {
matrix[i][k] = i;
}
}
for (i = 0; i < x; ++i) {
for (k = 0; k < y; ++k) {
printf("\t%d", matrix[k][i]);
}
printf("\n");
}
return matrix[i][k];
}
int turn()
{
int i = 0, k = 0;
int matrix[x][y];
for (i = 0; i < x; ++i) {
for (k = 0; k < y; ++k) {
matrix[i][k] = i;
}
}
for (i = 0; i < x; ++i) {
for (k = 0; k < y; ++k) {
printf("\t%d", matrix[i][k]);
}
printf("\n");
}
}
int main()
{
build();
printf("\t\n");
turn();
}
i want it to work for diffrent variables like x=5 and y=7.
My thought was to rotate the matrix by 90 degrees.
from
0 0 0 0
1 1 1 1
2 2 2 2
to
2 1 0
2 1 0
2 1 0
2 1 0

Answer 1

80% of work is declaring your functions and understanding what the declarations mean. You can start like this:
#define x 5
#define y 7
void build(int output[y][x]);
This declares a function build, which receives a matrix, and fills it with the needed data. Note: it doesn't return anything (i.e. returns void); instead of returning the data, it receives the pointer which it should write to. This is standard practice in C, because you cannot return arrays from functions.
I didn't write the code for it yet because it would distract you from understanding the flow of information in your program:
int main()
{
int matrix_before_rotation[y][x];
build(matrix_before_rotation);
}
This hypothetical program fills a matrix with values, using your function. It doesn't print it, but you could see the values if you used e.g. a debugger.
To declare a function which does the rotation:
void turn(int input[y][x], int output[x][y]);
Note the difference in dimensions, and the fact that the function receives two arguments - one for input, and one for output. You need to allocate two matrices in your main program:
int main()
{
int matrix_before_rotation[y][x];
int matrix_after_rotation[x][y];
build(matrix_before_rotation);
turn(matrix_before_rotation, matrix_after_rotation);
}
Given this code structure, it's easy to fill in the implementation details.
You might want to add a function for printing a matrix while you are debugging your program:
#define x 5
#define y 7
void build(int output[y][x]);
void turn(int input[y][x], int output[x][y]);
void print(int height, int width, int input[height][width]);
int main()
{
int matrix_before_rotation[y][x];
int matrix_after_rotation[x][y];
build(matrix_before_rotation);
print(y, x, matrix_before_rotation);
turn(matrix_before_rotation, matrix_after_rotation);
print(x, y, matrix_after_rotation);
}
Note: the printing function is more generic than the generating and the rotating functions - it knows how to work with matrices of any dimensions. You need it because you need at least two types of matrices in your new program - [7][5] and [5][7]. You can use this idea to generalize your rotating function so it could work with matrices of any dimensions.

Answer 2

Just a little modification to your code
#include <stdio.h>
#define x 3
#define y 4
int build() {
int i = 0, k = 0;
int matrix[x][y];
for (i = 0; i < x; ++i) {
for (k = 0; k < y; ++k) {
matrix[i][k] = i;
}
}
for (i = 0; i < x; ++i) {
for (k = 0; k < y; ++k) {
printf("\t%d", matrix[i][k]);
}
printf("\n");
}
return matrix[i][k];}
//for right turn you will have to modify the loop like this
int r_turn()
{
int i = 0, k = 0;
int matrix[x][y];
for(i=0; i<y; i++) //for outer loop, take y, because you're rotating
//loop , and y will come before x
{
for(k=x-1; k>=0; k--) //thereby, x goes after y
{
matrix[k][i] = k;
}
}
for(i=0; i<y; i++) //printing matrix in the same way we wrote
{
for(k=x-1; k>=0; k--) //here, k will start from k because
//index starts from 0
{
printf("\t%d", matrix[k][i]);
}
printf("\n");
}
}
int main()
{
build();
printf("\t\n");
r_turn();
}