leetcode — rotate-image

import java.util.Arrays;

/**
* Source : https://oj.leetcode.com/problems/rotate-image/ *
* Created by lverpeng on 2017/7/18.
*
* You are given an n x n 2D matrix representing an image.
* Rotate the image by 90 degrees (clockwise).
* Follow up:
* Could you do this in-place?
*
*/
public class RotateImage {

/**
* 将二维数组顺时针旋转90度
*
* 找到旋转前后的规律
*
* @param matrix
* @return
*/
public int[][] rotate (int[][] matrix) {
if (matrix.length == 0) {
return matrix;
}
int[][] rotatedMatrix = new int[matrix[0].length][matrix.length];
for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < matrix[0].length; j++) {
rotatedMatrix[j][i] = matrix[matrix.length - 1 - i][j];
}

}
return rotatedMatrix;
}

/**
* 如果矩阵是行列数相等
* 旋转矩阵，，矩阵有四条边，相当于四条边上的元素互换位置，1号换到2号，2号换到3号，3号换到4号，4号换到1号
*
*
* @param matrix
*/
public void rotate1 (int[][] matrix) {
if (matrix.length == 0) {
return;
}
int length = matrix.length;
for (int i = 0; i < length / 2; i++) {
for (int j = i; j < length - i -1 ; j++) {
int temp = matrix[i][j];
matrix[i][j] = matrix[length -1 -j][i];
matrix[length -1 -j][i] = matrix[length - 1 - i][length - 1 - j];
matrix[length - 1 - i][length - 1 - j] = matrix[j][length - 1 - i];
matrix[j][length - 1 - i] = temp;
}

}
}

public static void printMatrix (int[][] matrix) {
for (int i = 0; i < matrix.length; i++) {
System.out.println(Arrays.toString(matrix[i]));
}
System.out.println();
}

public static void main(String[] args) {
RotateImage rotateImage = new RotateImage();
int[][] matrix = new int[][]{
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
int[][] matrix1 = new int[][]{
{1, 2, 3},
{4, 5, 6},
{7, 8, 9},
{10, 11, 12}
};
int[][] matrix2 = new int[][]{
{1, 2, 3},
{4, 5, 6}
};
int[][] matrix3 = new int[][]{
{1, 2, 3}
};
int[][] matrix4 = new int[][]{
{1},
{4},
{5}
};

int[][] matrix5 = new int[][]{};

int[][] matrix6 = new int[][]{{},{}};

printMatrix(rotateImage.rotate(matrix));
printMatrix(rotateImage.rotate(matrix1));
printMatrix(rotateImage.rotate(matrix2));
printMatrix(rotateImage.rotate(matrix3));
printMatrix(rotateImage.rotate(matrix4));
printMatrix(rotateImage.rotate(matrix5));
printMatrix(rotateImage.rotate(matrix6));

System.out.println("========rotate1========");
int[][] matrix7 = new int[][]{
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
rotateImage.rotate1(matrix7);
printMatrix(matrix7);

int[][] matrix8 = new int[][]{
{1, 2, 3, 4},
{5, 6, 7, 8},
{9, 10, 11, 12},
{13, 14, 15, 16}
};
rotateImage.rotate1(matrix8);
printMatrix(matrix8);

int[][] matrix9 = new int[][]{
{1}
};
rotateImage.rotate1(matrix9);
printMatrix(matrix9);
}
}