Java Program to Rotate all Matrix elements except the diagonal K times by 90 degrees in clockwise direction
Last Updated :
24 Jul, 2022
Given a square matrix mat[][] of dimension N and an integer K, the task is to rotate the matrix by 90 degrees K times without changing the position of the diagonal elements.
Examples:
Input: mat[][] = {{1, 2, 3, 4, 5}, {6, 7, 8, 9, 10}, {11, 12, 13, 14, 15}, {16, 17, 18, 19, 20}, {21, 22, 23, 24, 25}}, K = 1
Output:
1 16 11 6 5
22 7 12 9 2
23 18 13 8 3
24 17 14 19 4
21 20 15 10 25
Input: mat[][] = {{10, 11}, {12, 13}}, K = 2
Output:
10 11
12 13
Approach: The given problem can be solved by using the idea discussed in this article and the fact that the matrix restores after performing clockwise rotation 4 times. Follow the below steps to solve the given problem:
- Update the value of K as K % 4.
- Iterate until K is a positive and perform the following steps:
- Traverse the matrix, for i over the range [0, N / 2) and j over the range[0, N – i – 1) and perform the following steps:
- If the value of i != j and (i + j) != (N – 1), then perform the following steps:
- Store the value of mat[i][j] in a temporary variable temp.
- Update the value of mat[i][j] as mat[N – 1 – j][i].
- Update the value of mat[N – 1 – j][i] as mat[N – 1 -i][N – 1 – j].
- Update the value of mat[N – 1 – i][N – 1 – j] as mat[j][N – 1 – i].
- Update the value of mat[j][N – 1 – i] as temp.
- After completing the above steps, print the updated matrix obtained.
Below is the implementation of the above approach:
Java
import java.io.*;
import java.lang.*;
import java.util.*;
public class GFG {
static void print( int mat[][])
{
for ( int i = 0 ; i < mat.length; i++) {
for ( int j = 0 ; j < mat[ 0 ].length; j++)
System.out.print(mat[i][j] + " " );
System.out.println();
}
}
static void performSwap( int mat[][], int i, int j)
{
int N = mat.length;
int ei = N - 1 - i;
int ej = N - 1 - j;
int temp = mat[i][j];
mat[i][j] = mat[ej][i];
mat[ej][i] = mat[ei][ej];
mat[ei][ej] = mat[j][ei];
mat[j][ei] = temp;
}
static void rotate( int mat[][], int N, int K)
{
K = K % 4 ;
while (K-- > 0 ) {
for ( int i = 0 ; i < N / 2 ; i++) {
for ( int j = i; j < N - i - 1 ; j++) {
if (i != j && (i + j) != N - 1 ) {
performSwap(mat, i, j);
}
}
}
}
print(mat);
}
public static void main(String[] args)
{
int K = 5 ;
int mat[][] = {
{ 1 , 2 , 3 , 4 },
{ 6 , 7 , 8 , 9 },
{ 11 , 12 , 13 , 14 },
{ 16 , 17 , 18 , 19 },
};
int N = mat.length;
rotate(mat, N, K);
}
}
|
Output:
1 11 6 4
17 7 8 2
18 12 13 3
16 14 9 19
Time Complexity: O(N3) since using three inner loop one while and two for loop
Auxiliary Space: O(1)
Please refer complete article on Rotate all Matrix elements except the diagonal K times by 90 degrees in clockwise direction for more details!
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