c++ 2 dimension array rotation - c++

Question

I am writing a program in C++ to display a 2 dimensional array and then rotate it 90, 180, and 270 degrees. The array is a capital 'E' made of E's and blanks. I have written the program but when I run it it does print the E's rotated but vertically (top to bottom), my professor wants them rotated but to print horizontally (left to right).
By my logic I would have to edit my code to do:
-> print array row 1
-> rotate90
-> print array row 1
-> rotate90 (to revert to original)
-> rotate180
-> print array row 1
-> rotate180 (original)
-> rotate270
-> print array row 1
-> rotate 270 (original) ->
...continue 7 times until all rows are printed.
I know there is an easier way but I can't wrap my head around how to do it.
#include <iostream>
using namespace std;
char eArray[][7]{
{'E','E','E','E','E','E','E'},
{'E',' ',' ',' ',' ',' ',' '},
{'E',' ',' ',' ',' ',' ',' '},
{'E','E','E','E','E',' ',' '},
{'E',' ',' ',' ',' ',' ',' '},
{'E',' ',' ',' ',' ',' ',' '},
{'E','E','E','E','E','E','E'},
};
int n = 7;
void rotateArray90(char a[][7]){
for (int i = 0; i < n; i += 1) {
for (int j = i+1; j < n; j += 1) {
swap(eArray[i][j], eArray[j][i]);
}}}
void flipArray180(char a[][7]){
for (int i = 0; i < n; i += 1) {
for (int j = 0; j < n/2; j += 1) {
swap(eArray[i][j], eArray[i][n-1-j]);
}}}
void rotateArray270(char a[][7]){
for (int i = 0; i < n; i += 1) {
for (int j = 0; j < n/2; j += 1) {
swap(eArray[i][j], eArray[n-1-i][j]);
}}}
void printArray(char a[][7]){
for (int i = 0; i < n; ++i){
for (int j = 0; j < n; ++j){
cout << eArray[i][j] <<" ";
}cout << endl;
}}
int main(){
printArray(eArray);
cout <<"\n";
rotateArray90(eArray);
printArray(eArray);
cout <<"\n";
rotateArray90(eArray);
flipArray180(eArray);
printArray(eArray);
cout <<"\n";
flipArray180(eArray);
rotateArray270(eArray);
printArray(eArray);
cout <<"\n";
rotateArray270(eArray);
}
Thank you for the help.

Answer 1

I am not sure I got you, but what you doing here is not a rotation (in the sense of matrix rotations). When you apply rotateArray90(eArray) two times you should get your array rotated 180 degrees, but instead it turns back to original array.
Here is my rotation method, take a look whether it helps. When you use it, you do not need separate methods for rotating at 180, 270 etc degrees, you just applies it 2, 3, ... times. After 4th rotation array returns back to original. It works with any rectangle array, not only n x n. And you do not have to use raw pointers, use instead containers.
template<typename T>
void printArray(const vector<vector<T>> &vch) {
for (int i = 0; i < vch.size(); ++i) {
for (int j = 0; j < vch[0].size(); ++j) {
cout << vch[i][j] << " ";
}
cout << endl;
}
}
template<typename T>
void rotateArray(vector<vector<T>> &v)
{
vector<vector<T>>rotated;
for (size_t i = 0; i < v[0].size(); i++) {
vector<T> newRow;
for (int j = v.size() - 1; j >=0; j--) {
newRow.push_back(v[j][i]);
}
rotated.push_back(newRow);
}
v = rotated;
}
Here is an example how to use:
int main() {
vector<vector<char>> vch = {
{'E', 'E', 'E', 'E', 'E', 'E', 'E'},
{ 'E',' ',' ',' ',' ',' ',' ' },
{ 'E',' ',' ',' ',' ',' ',' ' },
{ 'E','E','E','E','E',' ',' ' },
{ 'E',' ',' ',' ',' ',' ',' ' },
{ 'E',' ',' ',' ',' ',' ',' ' },
{ 'E','E','E','E','E','E','E' },
};
printArray<char>(vch);
cout << "\n";
rotateArray<char>(vch);
printArray<char>(vch);
cout << "\n";
rotateArray<char>(vch);
printArray<char>(vch);
cout << "\n";
rotateArray<char>(vch);
printArray<char>(vch);
cout << "\n";
return 0;
}
//orignal
E E E E E E E
E
E
E E E E E
E
E
E E E E E E E
// rotated 90
E E E E E E E
E E E
E E E
E E E
E E E
E E
E E
// rotated 180
E E E E E E E
E
E
E E E E E
E
E
E E E E E E E
// rotated 270
E E
E E
E E E
E E E
E E E
E E E
E E E E E E E
// rotated 360
E E E E E E E
E
E
E E E E E
E
E
E E E E E E E