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Author: liwentian

README.md

@@ -271,7 +271,7 @@
 |384|[Shuffle an Array](https://leetcode.com/problems/shuffle-an-array/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/ShuffleAnArray.java)|75|
 |387|[First Unique Character in a String](https://leetcode.com/problems/first-unique-character-in-a-string/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/FirstUniqueCharacterInAString.java)|100|
 |388|[Longest Absolute File Path](https://leetcode.com/problems/longest-absolute-file-path/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/LongestAbsoluteFilePath.java)|65|其实不难，乍看没思路，多做几遍|
-|391|[Perfect Rectangle](https://leetcode.com/problems/perfect-rectangle/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/PerfectRectangle.java)||
+|391|[Perfect Rectangle](https://leetcode.com/problems/perfect-rectangle/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/PerfectRectangle.java)|70|这题很trick，多做两遍|
 |393|[UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/UTFValidation.java)|60|错了很多次，多做几遍|
 |394|[Decode String](https://leetcode.com/problems/decode-string/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/DecodeString.java)|75|这题容易错，多做四遍|
 |395|[Longest Substring with At Least K Repeating Characters](https://leetcode.com/problems/longest-substring-with-at-least-k-repeating-characters/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/LongestSubstringWithAtLeastKRepeatingCharacters.java)|65|

google/src/main/java/com/leetcode/google/PerfectRectangle.java

@@ -0,0 +1,67 @@
+package com.leetcode.google;
+
+import java.util.HashMap;
+import java.util.HashSet;
+
+/**
+ * Created by liwentian on 2017/8/31.
+ */
+
+public class PerfectRectangle {
+
+    public boolean isRectangleCover(int[][] rectangles) {
+
+        int x1 = Integer.MAX_VALUE, y1 = Integer.MAX_VALUE;
+        int x2 = 0, y2 = 0;
+
+        HashSet<String> set = new HashSet<>();
+
+        int area = 0;
+
+        for (int[] rect : rectangles) {
+            int left = rect[0];
+            int bottom = rect[1];
+            int right = rect[2];
+            int top = rect[3];
+
+            area += (right - left) * (top - bottom);
+
+            x1 = Math.min(left, x1);
+            y1 = Math.min(bottom, y1);
+            x2 = Math.max(right, x2);
+            y2 = Math.max(top, y2);
+
+            String s1 = left + "." + bottom;
+            String s2 = left + "." + top;
+            String s3 = right + "." + bottom;
+            String s4 = right + "." + top;
+
+            if (!set.add(s1)) {
+                set.remove(s1);
+            }
+
+            if (!set.add(s2)) {
+                set.remove(s2);
+            }
+
+            if (!set.add(s3)) {
+                set.remove(s3);
+            }
+
+            if (!set.add(s4)) {
+                set.remove(s4);
+            }
+        }
+
+        String s1 = x1 + "." + y1;
+        String s2 = x1 + "." + y2;
+        String s3 = x2 + "." + y1;
+        String s4 = x2 + "." + y2;
+
+        if (!set.contains(s1) || !set.contains(s2) || !set.contains(s3) || !set.contains(s4) || set.size() != 4) {
+            return false;
+        }
+
+        return area == (x2 - x1) * (y2 - y1);
+    }
+}