add

feiyutalk · feiyutalk · commit f5e2c4dcf00d · 2018-05-12T23:22:21.000+08:00
diff --git a/problems/202. Happy Number/README.md b/problems/202. Happy Number/README.md
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+# 202. Happy Number
+
+## #1 除于取余[AC]
+
+### 算法
+
+```java
+class Solution {
+    public boolean isHappy(int n) {
+        Set<Integer> set = new HashSet<>();
+        int remain = 0, sum = 0;
+        while(set.add(n)){
+            sum = 0;
+            while(n > 0){
+                remain = n % 10;
+                sum += remain*remain;
+                n /= 10;
+            }
+            if(sum == 1)
+                return true;
+            else
+                n = sum;
+        }
+        return false;
+    }
+}
+```
+
diff --git a/problems/223. Rectangle Area/README.md b/problems/223. Rectangle Area/README.md
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+# 223. Rectangle Area
+
+## #1 分类整合[AC]
+
+### 思路
+
+要求两个矩形在2D平面上的面积$S$，我们对$S$进行分解拆成，$S = S_{r_1} + S_{r_2} -S_{inter}$，其中$S_{r_1}$表示第一个矩形的面积；$S_{r_2}$表示第二个矩形的面积；$S_{inter}$表示两个矩形相交的面积。
+
+### 算法
+
+```java
+class Solution {
+    public int computeArea(int A, int B, int C, int D, int E, int F, int G, int H) {
+        long bl1 = Math.max(A, E);
+        long bl2 = Math.max(B, F);
+        long tr1 = Math.min(C, G);
+        long tr2 = Math.min(D, H);
+        long inter =  Math.max(tr1 - bl1, 0) * Math.max(tr2 - bl2, 0);
+        long rec1 = (C - A) * (D - B);
+        long rec2 = (G - E) * (H - F);
+        return (int)(rec1 + rec2 - inter);
+    }
+}
+```
+
+### 复杂度分析
+
+- 时间复杂度：$O(1)$
+- 空间复杂度：$O(1)$
+
