add 832

fishercoder1534 · fishercoder1534 · commit c0a800302758 · 2018-05-13T09:40:37.000-07:00
diff --git a/README.md b/README.md
@@ -22,6 +22,7 @@ Your ideas/fixes/algorithms are more than welcome!
 
 |  #  |      Title     |   Solutions   | Time          | Space         | Video  | Difficulty  | Tag                   
 |-----|----------------|---------------|---------------|---------------|--------|-------------|-------------
+|832|[Flipping an Image](https://leetcode.com/problems/flipping-an-image/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_832.java) | O(n) | O(1) | |Easy|
 |830|[Positions of Large Groups](https://leetcode.com/problems/positions-of-large-groups/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_830.java) | O(n) | O(n) | |Easy|
 |824|[Goat Latin](https://leetcode.com/problems/goat-latin/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_824.java) | O(n) | O(1) | |Easy| 
 |821|[Shortest Distance to a Character](https://leetcode.com/problems/shortest-distance-to-a-character/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_821.java) | O(n) | O(k) (k is the number of char C in S) | |Easy| 
diff --git a/src/main/java/com/fishercoder/solutions/_832.java b/src/main/java/com/fishercoder/solutions/_832.java
@@ -0,0 +1,60 @@
+package com.fishercoder.solutions;
+
+/**
+ * 832. Flipping an Image
+ *
+ * Given a binary matrix A, we want to flip the image horizontally, then invert it, and return the resulting image.
+ * To flip an image horizontally means that each row of the image is reversed.  For example, flipping [1, 1, 0] horizontally results in [0, 1, 1].
+ * To invert an image means that each 0 is replaced by 1, and each 1 is replaced by 0. For example, inverting [0, 1, 1] results in [1, 0, 0].
+ *
+ * Example 1:
+ * Input: [[1,1,0],[1,0,1],[0,0,0]]
+ * Output: [[1,0,0],[0,1,0],[1,1,1]]
+ * Explanation: First reverse each row: [[0,1,1],[1,0,1],[0,0,0]].
+ * Then, invert the image: [[1,0,0],[0,1,0],[1,1,1]]
+ *
+ * Example 2:
+ * Input: [[1,1,0,0],[1,0,0,1],[0,1,1,1],[1,0,1,0]]
+ * Output: [[1,1,0,0],[0,1,1,0],[0,0,0,1],[1,0,1,0]]
+ * Explanation: First reverse each row: [[0,0,1,1],[1,0,0,1],[1,1,1,0],[0,1,0,1]].
+ * Then invert the image: [[1,1,0,0],[0,1,1,0],[0,0,0,1],[1,0,1,0]]
+ *
+ * Notes:
+ * 1 <= A.length = A[0].length <= 20
+ * 0 <= A[i][j] <= 1
+ */
+public class _832 {
+  public static class Solution1 {
+    public int[][] flipAndInvertImage(int[][] A) {
+      int m = A.length;
+      int n = A[0].length;
+      int[][] result = new int[m][n];
+      for (int i = 0; i < m; i++) {
+        int[] flipped = (reverse(A[i]));
+        result[i] = invert(flipped);
+      }
+      return result;
+    }
+
+    private int[] invert(int[] flipped) {
+      int[] result = new int[flipped.length];
+      for (int i = 0; i < flipped.length; i++) {
+        if (flipped[i] == 0) {
+          result[i] = 1;
+        } else {
+          result[i] = 0;
+        }
+      }
+      return result;
+    }
+
+    private int[] reverse(int[] nums) {
+      for (int i = 0, j = nums.length - 1; i < j; i++, j--) {
+        int tmp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = tmp;
+      }
+      return nums;
+    }
+  }
+}
diff --git a/src/test/java/com/fishercoder/_832Test.java b/src/test/java/com/fishercoder/_832Test.java
@@ -0,0 +1,50 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._832;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertArrayEquals;
+
+public class _832Test {
+  private static _832.Solution1 solution1;
+  private static int[][] expected;
+  private static int[][] A;
+
+  @BeforeClass
+  public static void setup() {
+    solution1 = new _832.Solution1();
+  }
+
+  @Test
+  public void test1() {
+    A = new int[][] {
+        {1, 1, 0},
+        {1, 0, 1},
+        {0, 0, 0}
+    };
+    expected = new int[][] {
+        {1, 0, 0},
+        {0, 1, 0},
+        {1, 1, 1}
+    };
+    assertArrayEquals(expected, solution1.flipAndInvertImage(A));
+  }
+
+  @Test
+  public void test2() {
+    A = new int[][] {
+        {1, 1, 0, 0},
+        {1, 0, 0, 1},
+        {0, 1, 1, 1},
+        {1, 0, 1, 0}
+    };
+    expected = new int[][] {
+        {1, 1, 0, 0},
+        {0, 1, 1, 0},
+        {0, 0, 0, 1},
+        {1, 0, 1, 0}
+    };
+    assertArrayEquals(expected, solution1.flipAndInvertImage(A));
+  }
+}
