feat: add python and java solutions to lcof question

添加《剑指 Offer》题解：面试题41. 数据流中的中位数

Author: yanglbme

lcof/README.md

@@ -55,7 +55,7 @@
 |  [45](https://leetcode-cn.com/problems/ba-shu-zu-pai-cheng-zui-xiao-de-shu-lcof)  |  [把数组排成最小的数](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9845.%20%E6%8A%8A%E6%95%B0%E7%BB%84%E6%8E%92%E6%88%90%E6%9C%80%E5%B0%8F%E7%9A%84%E6%95%B0/README.md)  |  `排序`  |  中等  |
 |  [46](https://leetcode-cn.com/problems/ba-shu-zi-fan-yi-cheng-zi-fu-chuan-lcof)  |  [把数字翻译成字符串](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9846.%20%E6%8A%8A%E6%95%B0%E5%AD%97%E7%BF%BB%E8%AF%91%E6%88%90%E5%AD%97%E7%AC%A6%E4%B8%B2/README.md)  |    |  中等  |
 |  [47](https://leetcode-cn.com/problems/li-wu-de-zui-da-jie-zhi-lcof)  |  [礼物的最大价值](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9847.%20%E7%A4%BC%E7%89%A9%E7%9A%84%E6%9C%80%E5%A4%A7%E4%BB%B7%E5%80%BC/README.md)  |  `动态规划`  |  中等  |
-|  [48](https://leetcode-cn.com/problems/zui-chang-bu-han-zhong-fu-zi-fu-de-zi-zi-fu-chuan-lcof)  |  [最长不含重复字符的子字符串](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9848.%20%E6%9C%80%E9%95%BF%E4%B8%8D%E5%90%AB%E9%87%8D%E5%A4%8D%E5%AD%97%E7%AC%A6%E7%9A%84%E5%AD%90%E5%AD%97%E7%AC%A6%E4%B8%B2/README.md)  |  `哈希表`,`双指针`,`None`  |  中等  |
+|  [48](https://leetcode-cn.com/problems/zui-chang-bu-han-zhong-fu-zi-fu-de-zi-zi-fu-chuan-lcof)  |  [最长不含重复字符的子字符串](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9848.%20%E6%9C%80%E9%95%BF%E4%B8%8D%E5%90%AB%E9%87%8D%E5%A4%8D%E5%AD%97%E7%AC%A6%E7%9A%84%E5%AD%90%E5%AD%97%E7%AC%A6%E4%B8%B2/README.md)  |  `哈希表`,`双指针`  |  中等  |
 |  [49](https://leetcode-cn.com/problems/chou-shu-lcof)  |  [丑数](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9849.%20%E4%B8%91%E6%95%B0/README.md)  |  `数学`  |  中等  |
 |  [50](https://leetcode-cn.com/problems/di-yi-ge-zhi-chu-xian-yi-ci-de-zi-fu-lcof)  |  [第一个只出现一次的字符](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9850.%20%E7%AC%AC%E4%B8%80%E4%B8%AA%E5%8F%AA%E5%87%BA%E7%8E%B0%E4%B8%80%E6%AC%A1%E7%9A%84%E5%AD%97%E7%AC%A6/README.md)  |  `哈希表`  |  简单  |
 |  [51](https://leetcode-cn.com/problems/shu-zu-zhong-de-ni-xu-dui-lcof)  |  [数组中的逆序对](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9851.%20%E6%95%B0%E7%BB%84%E4%B8%AD%E7%9A%84%E9%80%86%E5%BA%8F%E5%AF%B9/README.md)  |    |  困难  |
@@ -71,8 +71,8 @@
 |  [57 - II](https://leetcode-cn.com/problems/he-wei-sde-lian-xu-zheng-shu-xu-lie-lcof)  |  [和为s的连续正数序列](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9857%20-%20II.%20%E5%92%8C%E4%B8%BAs%E7%9A%84%E8%BF%9E%E7%BB%AD%E6%AD%A3%E6%95%B0%E5%BA%8F%E5%88%97/README.md)  |    |  简单  |
 |  [58 - I](https://leetcode-cn.com/problems/fan-zhuan-dan-ci-shun-xu-lcof)  |  [翻转单词顺序](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9858%20-%20I.%20%E7%BF%BB%E8%BD%AC%E5%8D%95%E8%AF%8D%E9%A1%BA%E5%BA%8F/README.md)  |  `字符串`  |  简单  |
 |  [58 - II](https://leetcode-cn.com/problems/zuo-xuan-zhuan-zi-fu-chuan-lcof)  |  [左旋转字符串](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9858%20-%20II.%20%E5%B7%A6%E6%97%8B%E8%BD%AC%E5%AD%97%E7%AC%A6%E4%B8%B2/README.md)  |  `字符串`  |  简单  |
-|  [59 - I](https://leetcode-cn.com/problems/hua-dong-chuang-kou-de-zui-da-zhi-lcof)  |  [滑动窗口的最大值](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9859%20-%20I.%20%E6%BB%91%E5%8A%A8%E7%AA%97%E5%8F%A3%E7%9A%84%E6%9C%80%E5%A4%A7%E5%80%BC/README.md)  |  `栈`,`None`  |  简单  |
-|  [59 - II](https://leetcode-cn.com/problems/dui-lie-de-zui-da-zhi-lcof)  |  [队列的最大值](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9859%20-%20II.%20%E9%98%9F%E5%88%97%E7%9A%84%E6%9C%80%E5%A4%A7%E5%80%BC/README.md)  |  `栈`,`None`  |  中等  |
+|  [59 - I](https://leetcode-cn.com/problems/hua-dong-chuang-kou-de-zui-da-zhi-lcof)  |  [滑动窗口的最大值](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9859%20-%20I.%20%E6%BB%91%E5%8A%A8%E7%AA%97%E5%8F%A3%E7%9A%84%E6%9C%80%E5%A4%A7%E5%80%BC/README.md)  |  `栈`  |  简单  |
+|  [59 - II](https://leetcode-cn.com/problems/dui-lie-de-zui-da-zhi-lcof)  |  [队列的最大值](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9859%20-%20II.%20%E9%98%9F%E5%88%97%E7%9A%84%E6%9C%80%E5%A4%A7%E5%80%BC/README.md)  |  `栈`  |  中等  |
 |  [60](https://leetcode-cn.com/problems/nge-tou-zi-de-dian-shu-lcof)  |  [n个骰子的点数](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9860.%20n%E4%B8%AA%E9%AA%B0%E5%AD%90%E7%9A%84%E7%82%B9%E6%95%B0/README.md)  |    |  简单  |
 |  [61](https://leetcode-cn.com/problems/bu-ke-pai-zhong-de-shun-zi-lcof)  |  [扑克牌中的顺子](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9861.%20%E6%89%91%E5%85%8B%E7%89%8C%E4%B8%AD%E7%9A%84%E9%A1%BA%E5%AD%90/README.md)  |    |  简单  |
 |  [62](https://leetcode-cn.com/problems/yuan-quan-zhong-zui-hou-sheng-xia-de-shu-zi-lcof)  |  [圆圈中最后剩下的数字](/lcof/%E9%9D%A2%E8%AF%95%E9%A2%9862.%20%E5%9C%86%E5%9C%88%E4%B8%AD%E6%9C%80%E5%90%8E%E5%89%A9%E4%B8%8B%E7%9A%84%E6%95%B0%E5%AD%97/README.md)  |    |  简单  |

lcof/面试题41. 数据流中的中位数/README.md

@@ -41,20 +41,81 @@
 
 ## 解法
 <!-- 这里可写通用的实现逻辑 -->
-
+- 创建大根堆、小根堆，其中：大根堆存放较小的一半元素，小根堆存放较大的一半元素。
+- 添加元素时，若两堆元素个数相等，放入小根堆（使得小根堆个数多1）；若不等，放入大根堆（使得大小根堆元素个数相等）
+- 取中位数时，若两队元素个数相等，取两堆顶求平均值；若不等，取小根堆堆顶。
 
 ### Python3
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```python
+class MedianFinder:
+
+    def __init__(self):
+        """
+        initialize your data structure here.
+        """
+        self.max_heap = []
+        self.min_heap = []
+
+
+    def addNum(self, num: int) -> None:
+        if len(self.max_heap) == len(self.min_heap):
+            heapq.heappush(self.min_heap, -heapq.heappushpop(self.max_heap, -num))
+        else:
+            heapq.heappush(self.max_heap, -heapq.heappushpop(self.min_heap, num))
 
+    def findMedian(self) -> float:
+        return (-self.max_heap[0] + self.min_heap[0]) / 2 if len(self.max_heap) == len(self.min_heap) else self.min_heap[0]
+
+
+# Your MedianFinder object will be instantiated and called as such:
+# obj = MedianFinder()
+# obj.addNum(num)
+# param_2 = obj.findMedian()
 ```
 
 ### Java
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```java
-
+class MedianFinder {
+    Queue<Integer> minHeap;
+    Queue<Integer> maxHeap;
+
+    /** initialize your data structure here. */
+    public MedianFinder() {
+        minHeap = new PriorityQueue<>();
+        maxHeap = new PriorityQueue<>((a, b) -> b - a);
+    }
+    
+    public void addNum(int num) {
+        if (maxHeap.size() == minHeap.size()) {
+            maxHeap.offer(num);
+            // 放入小根堆(小根堆多1)
+            minHeap.offer(maxHeap.poll());
+        } else {
+            minHeap.offer(num);
+            // 放入大根堆(大小堆数量相等)
+            maxHeap.offer(minHeap.poll());
+        }
+    }
+    
+    public double findMedian() {
+        if (((maxHeap.size() + minHeap.size()) & 1) == 0) {
+            // 偶数个，取两个堆顶平均值
+            return (maxHeap.peek() + minHeap.peek()) / 2.0;
+        }
+        return minHeap.peek();
+    }
+}
+
+/**
+ * Your MedianFinder object will be instantiated and called as such:
+ * MedianFinder obj = new MedianFinder();
+ * obj.addNum(num);
+ * double param_2 = obj.findMedian();
+ */
 ```
 
 ### ...

lcof/面试题41. 数据流中的中位数/Solution.java

@@ -0,0 +1,37 @@
+class MedianFinder {
+    Queue<Integer> minHeap;
+    Queue<Integer> maxHeap;
+
+    /** initialize your data structure here. */
+    public MedianFinder() {
+        minHeap = new PriorityQueue<>();
+        maxHeap = new PriorityQueue<>((a, b) -> b - a);
+    }
+    
+    public void addNum(int num) {
+        if (maxHeap.size() == minHeap.size()) {
+            maxHeap.offer(num);
+            // 放入小根堆(小根堆多1)
+            minHeap.offer(maxHeap.poll());
+        } else {
+            minHeap.offer(num);
+            // 放入大根堆(大小堆数量相等)
+            maxHeap.offer(minHeap.poll());
+        }
+    }
+    
+    public double findMedian() {
+        if (((maxHeap.size() + minHeap.size()) & 1) == 0) {
+            // 偶数个，取两个堆顶平均值
+            return (maxHeap.peek() + minHeap.peek()) / 2.0;
+        }
+        return minHeap.peek();
+    }
+}
+
+/**
+ * Your MedianFinder object will be instantiated and called as such:
+ * MedianFinder obj = new MedianFinder();
+ * obj.addNum(num);
+ * double param_2 = obj.findMedian();
+ */

lcof/面试题41. 数据流中的中位数/Solution.py

@@ -0,0 +1,24 @@
+class MedianFinder:
+
+    def __init__(self):
+        """
+        initialize your data structure here.
+        """
+        self.max_heap = []
+        self.min_heap = []
+
+
+    def addNum(self, num: int) -> None:
+        if len(self.max_heap) == len(self.min_heap):
+            heapq.heappush(self.min_heap, -heapq.heappushpop(self.max_heap, -num))
+        else:
+            heapq.heappush(self.max_heap, -heapq.heappushpop(self.min_heap, num))
+
+    def findMedian(self) -> float:
+        return (-self.max_heap[0] + self.min_heap[0]) / 2 if len(self.max_heap) == len(self.min_heap) else self.min_heap[0]
+
+
+# Your MedianFinder object will be instantiated and called as such:
+# obj = MedianFinder()
+# obj.addNum(num)
+# param_2 = obj.findMedian()

lcof/面试题65. 不用加减乘除做加法/README.md

@@ -33,8 +33,7 @@ class Solution:
             s = a ^ b
             carry = ((a & b) << 1) & 0xffffffff
             a, b = s, carry
-        # 若a是正数，直接返回；若是负数，转为原码
-        return a if a < 0x80000000 else ~(a^0xffffffff)
+        return a if a < 0x80000000 else ~(a ^ 0xffffffff)
 ```
 
 ### Java

lcof/面试题65. 不用加减乘除做加法/Solution.py

@@ -6,4 +6,4 @@ def add(self, a: int, b: int) -> int:
             s = a ^ b
             carry = ((a & b) << 1) & 0xffffffff
             a, b = s, carry
-        return a if a < 0x80000000 else ~(a^0xffffffff)
+        return a if a < 0x80000000 else ~(a ^ 0xffffffff)