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  • 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);
        }
    }
    
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  • 原文地址:https://www.cnblogs.com/sunshine-2015/p/7503169.html
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