Rotate Image

1package pkg5leetcode.blind75;2 3/*4 * Rotate Image | LC 485 * APPROACH: Transpose then reverse each row for 90° clockwise.6 * COMPLEXITY: Time O(n^2), Space O(1)7 */8public class blind75_LC48RotateImage {9    static void rotate(int[][] matrix) {10        int n = matrix.length;11        for (int i = 0; i < n; i++)12            for (int j = i + 1; j < n; j++) {13                int t = matrix[i][j];14                matrix[i][j] = matrix[j][i];15                matrix[j][i] = t;16            }17        for (int i = 0; i < n; i++)18            for (int lo = 0, hi = n - 1; lo < hi; lo++, hi--) {19                int t = matrix[i][lo];20                matrix[i][lo] = matrix[i][hi];21                matrix[i][hi] = t;22            }23    }24 25    public static void main(String[] args) {26        int[][] m1 = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};27        rotate(m1);28        check(m1[0][0] == 7 && m1[0][2] == 1 && m1[2][0] == 9, "case1");29        int[][] m2 = {{5, 1, 9, 11}, {2, 4, 8, 10}, {13, 3, 6, 7}, {15, 14, 12, 16}};30        rotate(m2);31        check(m2[0][0] == 15 && m2[3][3] == 11, "case2");32        System.out.println("all tests passed");33    }34 35    static void check(boolean cond, String name) {36        if (!cond) throw new AssertionError("FAILED: " + name);37        System.out.println("  PASS " + name);38    }39}