Merge branch 'master' of https://github.com/azl397985856/leetcode

redzealot2008 · Jun 28, 2019 · 90d9424 · 90d9424
2 parents 176f37f + 7f799b8
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diff --git a/assets/problems/191.number-of-1-bits.png b/assets/problems/191.number-of-1-bits.png
diff --git a/problems/191.number-of-1-bits.md b/problems/191.number-of-1-bits.md
@@ -52,6 +52,10 @@ In Java, the compiler represents the signed integers using 2's complement notati
 
 ## 代码
 
+语言支持：JS, C++
+
+JavaScript Code:
+
 ```js
 /*
  * @lc app=leetcode id=191 lang=javascript
@@ -132,4 +136,49 @@ var hammingWeight = function(n) {
   return count;
 };
 
-```
+```
+C++ code:
+```c++
+class Solution {
+public:
+    int hammingWeight(uint32_t v) {
+        auto count = 0;
+        while (v != 0) {
+            v &= (v - 1);
+            ++count;
+        }
+        return count;
+    }
+};
+```
+
+## 扩展
+可以使用位操作来达到目的。例如8位的整数21:
+
+![number-of-1-bits](../assets/problems/191.number-of-1-bits.png)
+
+C++ Code：
+```c++
+const uint32_t ODD_BIT_MASK = 0xAAAAAAAA;
+const uint32_t EVEN_BIT_MASK = 0x55555555;
+const uint32_t ODD_2BIT_MASK = 0xCCCCCCCC;
+const uint32_t EVEN_2BIT_MASK = 0x33333333;
+const uint32_t ODD_4BIT_MASK = 0xF0F0F0F0;
+const uint32_t EVEN_4BIT_MASK = 0x0F0F0F0F;
+const uint32_t ODD_8BIT_MASK = 0xFF00FF00;
+const uint32_t EVEN_8BIT_MASK = 0x00FF00FF;
+const uint32_t ODD_16BIT_MASK = 0xFFFF0000;
+const uint32_t EVEN_16BIT_MASK = 0x0000FFFF;
+
+class Solution {
+public:
+
+    int hammingWeight(uint32_t v) {
+        v = (v & EVEN_BIT_MASK) + ((v & ODD_BIT_MASK) >> 1);
+        v = (v & EVEN_2BIT_MASK) + ((v & ODD_2BIT_MASK) >> 2);
+        v = (v & EVEN_4BIT_MASK) + ((v & ODD_4BIT_MASK) >> 4);
+        v = (v & EVEN_8BIT_MASK) + ((v & ODD_8BIT_MASK) >> 8);
+        return (v & EVEN_16BIT_MASK) + ((v & ODD_16BIT_MASK) >> 16);
+    }
+};
+```
diff --git a/problems/92.reverse-linked-list-ii.md b/problems/92.reverse-linked-list-ii.md
@@ -49,6 +49,10 @@ Output: 1->4->3->2->5->NULL
 
 ## 代码
 
+语言支持：JS, C++
+
+JavaScript Code:
+
 ```js
 /*
  * @lc app=leetcode id=92 lang=javascript
@@ -142,3 +146,51 @@ var reverseBetween = function(head, m, n) {
 };
 
 ```
+C++ Code:
+```c++
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* reverseBetween(ListNode* head, int s, int e) {
+        if (s == e) return head;
+        ListNode* prev = nullptr;
+        auto cur = head;
+        for (int i = 1; i < s; ++i) {
+            prev = cur;
+            cur = cur->next;
+        }
+        // 此时各指针指向：
+        // x -> x -> x -> x  -> 1 -> 2 -> 3 -> 4 -> 5 -> 6 -> 7 -> 8 -> x -> x -> x ->
+        // ^head          ^prev ^cur
+        ListNode* p = nullptr;
+        auto c = cur;
+        auto tail = c;
+        ListNode* n = nullptr;
+        for (int i = s; i <= e; ++i) {
+            n = c->next;
+            c->next = p;
+            p = c;
+            c = n;
+        }
+        // 此时各指针指向：
+        // x -> x -> x -> x     8 -> 7 -> 6 -> 5 -> 4 -> 3 -> 2 -> 1     x -> x -> x ->
+        // ^head          ^prev ^p                                 ^cur  ^c
+        //                                                         ^tail
+        if (prev != nullptr) { // 若指向前一个节点的指针不为空，则说明s在链表中间（不是头节点）
+            prev->next = p;
+            cur->next = c;
+            return head;
+        } else {
+            if (tail != nullptr) tail->next = c;
+            return p;
+        }
+    }
+};
+```