leetcode

commit 48092c680db162869b6a39e8e372bbb0f1bfb399
parent a68605df316819569152e92b7d727f4ca8e2788f
Author: Jack Sangdahl <jack@pngu.org>
Date:   Sun,  3 May 2026 21:34:38 -0600

48. rotate image

Diffstat:
A
rotate_image.c
 | 
54
++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
rotate_image.py
 | 
35
+++++++++++++++++++++++++++++++++++

2 files changed, 89 insertions(+), 0 deletions(-)
diff --git a/rotate_image.c b/rotate_image.c
@@ -0,0 +1,54 @@
+// 48. Rotate Image
+#include "leetcode.h"
+
+/*
+ * you are given an 'n x n' 2d 'matrix' representing an image, rotate the image
+ * by 90 degrees (clockwise). you have to rotate the image in place, meaning you
+ * have to modify the input 2d matrix directly. do not allocate another 2d
+ * matrix and do the rotation.
+ */
+
+void rotate(int **matrix, int matrixSize, int *matrixColSize) {
+  int n = matrixSize;
+  for (int i = 0; i < n >> 1; i++)
+    for (int j = i; j < n - 1 - i; j++) {
+      int tmp = matrix[i][j];
+      matrix[i][j] = matrix[~j + n][i];
+      matrix[~j + n][i] = matrix[~i + n][~j + n];
+      matrix[~i + n][~j + n] = matrix[j][~i + n];
+      matrix[j][~i + n] = tmp;
+    }
+}
+
+int main() {
+  int m1i[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
+  int r1[3][3] = {{7, 4, 1}, {8, 5, 2}, {9, 6, 3}};
+  int m2i[4][4] = {
+      {5, 1, 9, 11}, {2, 4, 8, 10}, {13, 3, 6, 7}, {15, 14, 12, 16}};
+  int r2[4][4] = {
+      {15, 13, 2, 5}, {14, 3, 4, 1}, {12, 6, 8, 9}, {16, 7, 10, 11}};
+  struct two_d_arr *m1 =
+      two_d_arr_init(ARRAY_SIZE(m1i), ARRAY_SIZE(m1i[0]), m1i);
+  struct two_d_arr *m2 =
+      two_d_arr_init(ARRAY_SIZE(m2i), ARRAY_SIZE(m2i[0]), m2i);
+  rotate(m1->arr, m1->row_size, m1->col_size);
+  rotate(m2->arr, m2->row_size, m2->col_size);
+  for (int i = 0; i < m1->row_size; i++) {
+    for (int j = 0; j < m1->col_size[i]; j++) {
+      printf("%d ", m1->arr[i][j]);
+      assert(m1->arr[i][j] == r1[i][j]);
+    }
+    printf("\n");
+  }
+  printf("\n");
+  for (int i = 0; i < m2->row_size; i++) {
+    for (int j = 0; j < m2->col_size[i]; j++) {
+      printf("%d ", m2->arr[i][j]);
+      assert(m2->arr[i][j] == r2[i][j]);
+    }
+    printf("\n");
+  }
+  printf("\n");
+  two_d_arr_free(m1);
+  two_d_arr_free(m2);
+}
diff --git a/rotate_image.py b/rotate_image.py
@@ -0,0 +1,35 @@
+# 48. Rotate Image
+from typing import List
+
+"""
+you are given an 'n x n' 2d 'matrix' representing an image, rotate the image
+by 90 degrees (clockwise). you have to rotate the image in place, meaning you
+have to modify the input 2d matrix directly. do not allocate another 2d
+matrix and do the rotation.
+"""
+
+
+class Solution:
+    def rotate(self, matrix: List[List[int]]) -> None:
+        """
+        Do not return anything, modify matrix in-place instead.
+        """
+        n = len(matrix)
+        for i in range(n >> 1):
+            for j in range(i, n - 1 - i):
+                matrix[i][j], matrix[j][~i], matrix[~i][~j], matrix[~j][i] = (
+                    matrix[~j][i],
+                    matrix[i][j],
+                    matrix[j][~i],
+                    matrix[~i][~j],
+                )
+
+
+if __name__ == "__main__":
+    obj = Solution()
+    m1 = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
+    m2 = [[5, 1, 9, 11], [2, 4, 8, 10], [13, 3, 6, 7], [15, 14, 12, 16]]
+    obj.rotate(m1)
+    obj.rotate(m2)
+    print(m1)
+    print(m2)