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MatrixRotation.java
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MatrixRotation.java
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package by.andd3dfx.common;
/**
* <pre>
* <a href="https://www.hackerrank.com/challenges/matrix-rotation-algo/problem">Task description</a>
*
* You are given a 2D matrix of dimension m*n and a positive integer r. You have to rotate the matrix times and
* print the resultant matrix. Rotation should be in anti-clockwise direction.
* It is guaranteed that the minimum of m and n will be even.
*
* As an example, rotate the Start matrix by 2:
*
* Start First Second
* 1 2 3 4 2 3 4 5 3 4 5 6
* 12 1 2 5 -> 1 2 3 6 -> 2 3 4 7
* 11 4 3 6 12 1 4 7 1 2 1 8
* 10 9 8 7 11 10 9 8 12 11 10 9
* </pre>
*
* @see <a href="https://youtu.be/etkqSnthF4c">Video solution</a>
*/
public class MatrixRotation {
public static void rotate(int[][] matrix, int r) {
int left = 0;
int up = 0;
int m = matrix.length;
int n = matrix[0].length;
while (m >= 1 && n >= 1) {
var count = 2 * (m + n) - 4;
int[] tmp = new int[count];
int curr = 0;
for (int i = 0; i < n; i++) {
tmp[curr] = matrix[up][left + i];
curr++;
}
for (int i = 1; i < m - 1; i++) {
tmp[curr] = matrix[up + i][left + n - 1];
curr++;
}
for (int i = n - 1; i >= 0; i--) {
tmp[curr] = matrix[up + m - 1][left + i];
curr++;
}
for (int i = m - 2; i >= 1; i--) {
tmp[curr] = matrix[up + i][left];
curr++;
}
curr = r % count;
if (curr < 0) {
curr += count;
}
for (int i = 0; i < n; i++) {
matrix[up][left + i] = tmp[curr];
curr++;
if (curr >= count) {
curr -= count;
}
}
for (int i = 1; i < m - 1; i++) {
matrix[up + i][left + n - 1] = tmp[curr];
curr++;
if (curr >= count) {
curr -= count;
}
}
for (int i = n - 1; i >= 0; i--) {
matrix[up + m - 1][left + i] = tmp[curr];
curr++;
if (curr >= count) {
curr -= count;
}
}
for (int i = m - 2; i >= 1; i--) {
matrix[up + i][left] = tmp[curr];
curr++;
if (curr >= count) {
curr -= count;
}
}
m -= 2;
n -= 2;
left++;
up++;
}
}
}