rotate 90 degrees a matrix

version.cpp

// C++ program to rotate a matrix by 90 degrees 
#include <bits/stdc++.h> 
#define N 4 
using namespace std; 

void displayMatrix(int mat[N][N]); 

// An Inplace function to rotate a N x N matrix 
// by 90 degrees in anti-clockwise direction 
void rotateMatrix(int mat[][N]) 
{ 
	// Consider all squares one by one 
	for (int x = 0; x < N / 2; x++) { 
		// Consider elements in group of 4 in 
		// current square 
		for (int y = x; y < N - x - 1; y++) { 
			// store current cell in temp variable 
			int temp = mat[x][y]; 

			// move values from right to top 
			mat[x][y] = mat[y][N - 1 - x]; 

			// move values from bottom to right 
			mat[y][N - 1 - x] = mat[N - 1 - x][N - 1 - y]; 

			// move values from left to bottom 
			mat[N - 1 - x][N - 1 - y] = mat[N - 1 - y][x]; 

			// assign temp to left 
			mat[N - 1 - y][x] = temp; 
		} 
	} 
} 

// Function to print the matrix 
void displayMatrix(int mat[N][N]) 
{ 
	for (int i = 0; i < N; i++) { 
		for (int j = 0; j < N; j++) 
			printf("%2d ", mat[i][j]); 

		printf("\n"); 
	} 
	printf("\n"); 
} 

/* Driver program to test above functions */
int main() 
{ 
	// Test Case 1 
	int mat[N][N] = { 
		{ 1, 2, 3, 4 }, 
		{ 5, 6, 7, 8 }, 
		{ 9, 10, 11, 12 }, 
		{ 13, 14, 15, 16 } 
	}; 

	// Tese Case 2 
	/* int mat[N][N] = { 
						{1, 2, 3}, 
						{4, 5, 6}, 
						{7, 8, 9} 
					}; 
	*/

	// Tese Case 3 
	/*int mat[N][N] = { 
					{1, 2}, 
					{4, 5} 
				};*/

	// displayMatrix(mat); 

	rotateMatrix(mat); 

	// Print rotated matrix 
	displayMatrix(mat); 

	return 0; 
} 

version.py

# Python3 program to rotate a matrix by 90 degrees 
N = 4

# An Inplace function to rotate 
# N x N matrix by 90 degrees in 
# anti-clockwise direction 
def rotateMatrix(mat): 
	
	# Consider all squares one by one 
	for x in range(0, int(N / 2)): 
		
		# Consider elements in group 
		# of 4 in current square 
		for y in range(x, N-x-1): 
			
			# store current cell in temp variable 
			temp = mat[x][y] 

			# move values from right to top 
			mat[x][y] = mat[y][N-1-x] 

			# move values from bottom to right 
			mat[y][N-1-x] = mat[N-1-x][N-1-y] 

			# move values from left to bottom 
			mat[N-1-x][N-1-y] = mat[N-1-y][x] 

			# assign temp to left 
			mat[N-1-y][x] = temp 


# Function to print the matrix 
def displayMatrix( mat ): 
	
	for i in range(0, N): 
		
		for j in range(0, N): 
			
			print (mat[i][j], end = ' ') 
		print ("") 
	
	


# Driver Code 
mat = [[0 for x in range(N)] for y in range(N)] 

# Test case 1 
mat = [ [1, 2, 3, 4 ], 
		[5, 6, 7, 8 ], 
		[9, 10, 11, 12 ], 
		[13, 14, 15, 16 ] ] 
		
''' 
# Test case 2 
mat = [ [1, 2, 3 ], 
		[4, 5, 6 ], 
		[7, 8, 9 ] ] 

# Test case 3 
mat = [ [1, 2 ], 
		[4, 5 ] ] 
		
'''

rotateMatrix(mat) 

# Print rotated matrix 
displayMatrix(mat) 

Complexity Analysis:

Time Complexity : O(n*n), where n is side of array, A single traversal of the matrix is needed.
Space Complexity : O(1), constant space is needed