832_Flipping_an_Image

Author: qiyuangong

README.md

@@ -181,6 +181,7 @@ Also, there are open source implementations for basic data structs and algorithm
 | 804 | [Unique Morse Code Words](https://leetcode.com/problems/unique-morse-code-words/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/804_Unique_Morse_Code_Words.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/804_Unique_Morse_Code_Words.java) | String, Hash and Set. Set is recommended. |
 | 811 | [Subdomain Visit Count](https://leetcode.com/problems/subdomain-visit-count/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/811_Subdomain_Visit_Count.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/811_Subdomain_Visit_Count.java) | String split and HashMap, O(n) and O(n) |
 | 819 | [Most Common Word](https://leetcode.com/problems/most-common-word/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/819_Most_Common_Word.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/819_Most_Common_Word.java) | String processing, be careful about 'b,b,b'. regex is recommended. |
+| 832 | [Flipping an Image](https://leetcode.com/problems/flipping-an-image/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/832_Flipping_an_Image.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/832_Flipping_an_Image.java) | Invert and swap can be done at the same time, and careful about (n + 1)/2, O(n^2) and O(1) |
 | 844 | [Backspace String Compare](https://leetcode.com/problems/backspace-string-compare/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/844_Backspace_String_Compare.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/844_Backspace_String_Compare.java) | 1. Stack pop when encounters #, O(n) and O(n)<br>2. Compare string from end to start, O(n) and O(1) |
 | 852 | [Peak Index in a Mountain Array](https://leetcode.com/problems/peak-index-in-a-mountain-array/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/852_Peak_Index_in_a_Mountain_Array.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/852_Peak_Index_in_a_Mountain_Array.java) | 1. Scan the array until encountering decline, O(n) and O(1)<br>2. Binary seach with additional check for [i + 1], O(logn) and O(1) |
 | 867 | [Transpose Matrix](https://leetcode.com/problems/transpose-matrix/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/867_Transpose_Matrix.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/867_Transpose_Matrix.java) | Res[i][j] = A[j][i] |

java/832_Flipping_an_Image.java

@@ -0,0 +1,13 @@
+class Solution {
+    public int[][] flipAndInvertImage(int[][] A) {
+        int C = A[0].length;
+        for (int[] row: A)
+            for (int i = 0; i < (C + 1) / 2; ++i) {
+                int tmp = row[i] ^ 1;
+                row[i] = row[C - 1 - i] ^ 1;
+                row[C - 1 - i] = tmp;
+            }
+
+        return A;
+    }
+}

python/832_Flipping_an_Image.py

@@ -0,0 +1,11 @@
+class Solution(object):
+    def flipAndInvertImage(self, A):
+        for row in A:
+            for i in xrange((len(row) + 1) / 2):
+                """
+                In Python, the shortcut row[~i] = row[-i-1] = row[len(row) - 1 - i]
+                helps us find the i-th value of the row, counting from the right.
+                """
+                row[i], row[~i] = row[~i] ^ 1, row[i] ^ 1
+        return A
+        # return [[1 ^ i for i in row[::-1]] for row in A]