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package Stack; | ||
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import java.util.Iterator; | ||
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/** | ||
* 顺序栈的动态扩容 | ||
* Author: PeiJiaNi | ||
* @param <T> 顺序栈元素类型 | ||
*/ | ||
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public class DynamicStackBaseArray<T> implements Iterable<T> { | ||
private T[] items; // 数组 | ||
private int count; // 栈中的元素个数 | ||
private int length; // 栈空间大小 | ||
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/** | ||
* 初始化栈 | ||
* | ||
* @param length 栈空间大小 | ||
*/ | ||
public DynamicStackBaseArray(int length) { | ||
this.items = (T[]) new Object[length]; | ||
this.count = 0; | ||
this.length = length; | ||
} | ||
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/** | ||
* 入栈操作 平均时间复杂度O(1) | ||
* | ||
* @param item 入栈元素 | ||
*/ | ||
public void push(T item) { | ||
// 栈空间已满,则扩容 | ||
if (count == length) { | ||
resize(2 * items.length); | ||
} | ||
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items[count++] = item; | ||
} | ||
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/** | ||
* 出栈操作 平均时间复杂度O(1) | ||
* | ||
* @return 如果栈内不为空,则返回栈顶元素,否则返回-1 | ||
*/ | ||
public T pop() { | ||
if (count == 0) { | ||
System.out.println("当前栈已空,无法进行出栈操作"); | ||
return null; | ||
} | ||
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T item = items[--count]; | ||
items[count] = null; | ||
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if (count > 0 && (count == items.length / 4)) { | ||
resize(items.length / 2); | ||
} | ||
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// 返回下标为 count-1 的数组元素,并且栈中元素个数count-1 | ||
return item; | ||
} | ||
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/** | ||
* 栈空间动态增加或减小 | ||
* | ||
* @param size | ||
*/ | ||
private void resize(int size) { | ||
T[] newItems = (T[]) new Object[size]; | ||
for (int i = 0; i < count; i++) { | ||
newItems[i] = this.items[i]; | ||
} | ||
this.items = newItems; | ||
} | ||
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//返回栈中最近添加的元素而不删除它 | ||
public T peek() { | ||
return items[count - 1]; | ||
} | ||
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/** | ||
* 判断当前栈是否为空 | ||
* | ||
* @return 栈为空,则返回true,否则返回-1 | ||
*/ | ||
public boolean isEmpty() { | ||
return count == 0; | ||
} | ||
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/** | ||
* 返回栈中元素个数 | ||
* | ||
* @return | ||
*/ | ||
public int size() { | ||
return count; | ||
} | ||
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@Override | ||
public Iterator<T> iterator() { | ||
return new ArrayIterator(); | ||
} | ||
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// 内部类 | ||
class ArrayIterator implements Iterator { | ||
int numOfItems = count; | ||
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@Override | ||
public boolean hasNext() { | ||
return numOfItems > 0; | ||
} | ||
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@Override | ||
public T next() { | ||
return items[--numOfItems]; | ||
} | ||
} | ||
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public static void main(String[] args) { | ||
DynamicStackBaseArray<Integer> stack = new DynamicStackBaseArray<Integer>(6); | ||
stack.push(1); | ||
stack.push(2); | ||
stack.push(3); | ||
stack.push(4); | ||
stack.push(5); | ||
// System.out.println(stack.peek()); | ||
Iterator iterator = stack.iterator(); | ||
// System.out.println(iterator.hasNext()); | ||
while (iterator.hasNext()) { | ||
System.out.println(iterator.next()); | ||
} | ||
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} | ||
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} | ||
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# 数据结构和算法之美 | ||
# 请点击查看:[https://time.geekbang.org/column/intro/126](https://time.geekbang.org/column/intro/126) | ||
# 数据结构和算法必知必会的50个代码实现 | ||
### 微信搜索我的公众号“小争哥”,或者微信扫描下面二维码, 获取更多压箱底的干货分享 | ||
### 前Google工程师,5万+人跟着学的《数据结构和算法之美》专栏作者 | ||
![t2](https://github.com/wangzheng0822/markdownphotos/blob/master/pics/qrcode_for_gh_9b0e7afdff20_258.jpg) | ||
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## 数组 | ||
* 实现一个支持动态扩容的数组 | ||
* 实现一个大小固定的有序数组,支持动态增删改操作 | ||
* 实现两个有序数组合并为一个有序数组 | ||
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## 链表 | ||
* 实现单链表、循环链表、双向链表,支持增删操作 | ||
* 实现单链表反转 | ||
* 实现两个有序的链表合并为一个有序链表 | ||
* 实现求链表的中间结点 | ||
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## 栈 | ||
* 用数组实现一个顺序栈 | ||
* 用链表实现一个链式栈 | ||
* 编程模拟实现一个浏览器的前进、后退功能 | ||
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## 队列 | ||
* 用数组实现一个顺序队列 | ||
* 用链表实现一个链式队列 | ||
* 实现一个循环队列 | ||
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## 递归 | ||
* 编程实现斐波那契数列求值f(n)=f(n-1)+f(n-2) | ||
* 编程实现求阶乘n! | ||
* 编程实现一组数据集合的全排列 | ||
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## 排序 | ||
* 实现归并排序、快速排序、插入排序、冒泡排序、选择排序 | ||
* 编程实现O(n)时间复杂度内找到一组数据的第K大元素 | ||
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## 二分查找 | ||
* 实现一个有序数组的二分查找算法 | ||
* 实现模糊二分查找算法(比如大于等于给定值的第一个元素) | ||
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## 散列表 | ||
* 实现一个基于链表法解决冲突问题的散列表 | ||
* 实现一个LRU缓存淘汰算法 | ||
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## 字符串 | ||
* 实现一个字符集,只包含a~z这26个英文字母的Trie树 | ||
* 实现朴素的字符串匹配算法 | ||
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## 二叉树 | ||
* 实现一个二叉查找树,并且支持插入、删除、查找操作 | ||
* 实现查找二叉查找树中某个节点的后继、前驱节点 | ||
* 实现二叉树前、中、后序以及按层遍历 | ||
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## 堆 | ||
* 实现一个小顶堆、大顶堆、优先级队列 | ||
* 实现堆排序 | ||
* 利用优先级队列合并K个有序数组 | ||
* 求一组动态数据集合的最大Top K | ||
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## 图 | ||
* 实现有向图、无向图、有权图、无权图的邻接矩阵和邻接表表示方法 | ||
* 实现图的深度优先搜索、广度优先搜索 | ||
* 实现Dijkstra算法、A*算法 | ||
* 实现拓扑排序的Kahn算法、DFS算法 | ||
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## 回溯 | ||
* 利用回溯算法求解八皇后问题 | ||
* 利用回溯算法求解0-1背包问题 | ||
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## 分治 | ||
* 利用分治算法求一组数据的逆序对个数 | ||
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## 动态规划 | ||
* 0-1背包问题 | ||
* 最小路径和 | ||
* 编程实现莱文斯坦最短编辑距离 | ||
* 编程实现查找两个字符串的最长公共子序列 | ||
* 编程实现一个数据序列的最长递增子序列 |
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,64 @@ | ||
package Stack; | ||
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/** | ||
* 顺序栈(基于数组实现) | ||
* Author: PeiJiaNi | ||
*/ | ||
public class StackBaseArray { | ||
private int[] items; // 数组 | ||
private int count; // 栈中元素个数 | ||
private int length; // 栈空间大小 | ||
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public StackBaseArray(int capactiy) { | ||
this.items = new int[capactiy]; | ||
this.count = 0; | ||
this.length = capactiy; | ||
} | ||
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/** | ||
* 入栈操作 时间复杂度O(1) | ||
* @param item 要入栈的元素 | ||
* @return 入栈成功则返回true,否则返回false | ||
*/ | ||
public boolean push(int item) { | ||
if(count == length) { | ||
System.out.println("当前栈已满,无法进行入栈操作"); | ||
return false; | ||
} | ||
items[count] = item; | ||
++count; | ||
return true; | ||
} | ||
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/** | ||
* 出栈操作 时间复杂度O(1) | ||
* @return 如果栈内不为空,则返回栈顶元素,否则返回-1 | ||
*/ | ||
public int pop(){ | ||
if(count == 0) { | ||
System.out.println("当前栈已空,无法进行出栈操作"); | ||
return -1; | ||
} | ||
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// 返回下标为 count-1 的数组元素,并且栈中元素个数count-1 | ||
return items[--count]; | ||
} | ||
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public static void main(String[] args){ | ||
StackBaseArray stack = new StackBaseArray(6); | ||
stack.push(1); | ||
stack.push(2); | ||
stack.push(3); | ||
stack.push(4); | ||
stack.push(5); | ||
System.out.println(stack.pop()); | ||
System.out.println(stack.pop()); | ||
System.out.println(stack.pop()); | ||
System.out.println(stack.pop()); | ||
System.out.println(stack.pop()); | ||
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} | ||
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} | ||
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