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Commit 7f799b8

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raof01azl397985856
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‎problems/191.number-of-1-bits.md‎

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@@ -52,6 +52,10 @@ In Java, the compiler represents the signed integers using 2's complement notati
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## 代码
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语言支持:JS, C++
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JavaScript Code:
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```js
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/*
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* @lc app=leetcode id=191 lang=javascript
@@ -132,4 +136,49 @@ var hammingWeight = function(n) {
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return count;
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};
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```
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```
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C++ code:
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```c++
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class Solution {
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public:
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int hammingWeight(uint32_t v) {
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auto count = 0;
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while (v != 0) {
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v &= (v - 1);
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++count;
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}
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return count;
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}
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};
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```
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## 扩展
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可以使用位操作来达到目的。例如8位的整数21:
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![number-of-1-bits](../assets/problems/191.number-of-1-bits.png)
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C++ Code:
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```c++
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const uint32_t ODD_BIT_MASK = 0xAAAAAAAA;
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const uint32_t EVEN_BIT_MASK = 0x55555555;
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const uint32_t ODD_2BIT_MASK = 0xCCCCCCCC;
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const uint32_t EVEN_2BIT_MASK = 0x33333333;
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const uint32_t ODD_4BIT_MASK = 0xF0F0F0F0;
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const uint32_t EVEN_4BIT_MASK = 0x0F0F0F0F;
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const uint32_t ODD_8BIT_MASK = 0xFF00FF00;
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const uint32_t EVEN_8BIT_MASK = 0x00FF00FF;
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const uint32_t ODD_16BIT_MASK = 0xFFFF0000;
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const uint32_t EVEN_16BIT_MASK = 0x0000FFFF;
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class Solution {
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public:
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int hammingWeight(uint32_t v) {
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v = (v & EVEN_BIT_MASK) + ((v & ODD_BIT_MASK) >> 1);
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v = (v & EVEN_2BIT_MASK) + ((v & ODD_2BIT_MASK) >> 2);
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v = (v & EVEN_4BIT_MASK) + ((v & ODD_4BIT_MASK) >> 4);
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v = (v & EVEN_8BIT_MASK) + ((v & ODD_8BIT_MASK) >> 8);
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return (v & EVEN_16BIT_MASK) + ((v & ODD_16BIT_MASK) >> 16);
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}
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};
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```

‎problems/92.reverse-linked-list-ii.md‎

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@@ -49,6 +49,10 @@ Output: 1->4->3->2->5->NULL
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## 代码
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语言支持:JS, C++
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JavaScript Code:
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```js
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/*
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* @lc app=leetcode id=92 lang=javascript
@@ -142,3 +146,51 @@ var reverseBetween = function(head, m, n) {
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};
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```
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C++ Code:
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```c++
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/**
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* Definition for singly-linked list.
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* struct ListNode {
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* int val;
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* ListNode *next;
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* ListNode(int x) : val(x), next(NULL) {}
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* };
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*/
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class Solution {
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public:
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ListNode* reverseBetween(ListNode* head, int s, int e) {
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if (s == e) return head;
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ListNode* prev = nullptr;
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auto cur = head;
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for (int i = 1; i < s; ++i) {
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prev = cur;
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cur = cur->next;
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}
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// 此时各指针指向:
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// x -> x -> x -> x -> 1 -> 2 -> 3 -> 4 -> 5 -> 6 -> 7 -> 8 -> x -> x -> x ->
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// ^head ^prev ^cur
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ListNode* p = nullptr;
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auto c = cur;
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auto tail = c;
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ListNode* n = nullptr;
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for (int i = s; i <= e; ++i) {
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n = c->next;
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c->next = p;
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p = c;
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c = n;
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}
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// 此时各指针指向:
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// x -> x -> x -> x 8 -> 7 -> 6 -> 5 -> 4 -> 3 -> 2 -> 1 x -> x -> x ->
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// ^head ^prev ^p ^cur ^c
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// ^tail
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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)
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prev->next = p;
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cur->next = c;
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return head;
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} else {
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if (tail != nullptr) tail->next = c;
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return p;
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}
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}
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};
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```

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