Java兑现数据结构的栈和队列

Java实现数据结构的栈和队列
栈是一种先进后出的数据结构, 首先定义了栈需要实现的接口:

Java代码 

public interface MyStack {       /**       * 判断栈是否为空       */      boolean isEmpty();       /**       * 清空栈       */      void clear();       /**       * 栈的长度       */      int length();       /**       * 数据入栈       */      boolean push(T data);       /**       * 数据出栈       */      T pop();   }  public interface MyStack { /** * 判断栈是否为空 */ boolean isEmpty(); /** * 清空栈 */ void clear(); /** * 栈的长度 */ int length(); /** * 数据入栈 */ boolean push(T data); /** * 数据出栈 */ T pop(); }

栈的数组实现, 底层使用数组:

public class MyArrayStack implements MyStack {       private Object[] objs = new Object[16];       private int size = 0;         @Override      public boolean isEmpty() {           return size == 0;       }         @Override      public void clear() {           // 将数组中的数据置为null, 方便GC进行回收           for (int i = 0; i = objs.length) {               resize();           }           objs[size++] = data;           return true;       }         /**       * 数组扩容       */      private void resize() {           Object[] temp = new Object[objs.length * 3 / 2 + 1];           for (int i = 0; i  implements MyStack { private Object[] objs = new Object[16]; private int size = 0; @Override public boolean isEmpty() { return size == 0; } @Override public void clear() { // 将数组中的数据置为null, 方便GC进行回收 for (int i = 0; i = objs.length) { resize(); } objs[size++] = data; return true; } /** * 数组扩容 */ private void resize() { Object[] temp = new Object[objs.length * 3 / 2 + 1]; for (int i = 0; i  implements MyStack {       /**       * 栈顶指针       */      private Node top;       /**       * 栈的长度       */      private int size;              public MyLinkedStack() {           top = null;           size = 0;       }              @Override      public boolean isEmpty() {           return size == 0;       }              @Override      public void clear() {           top = null;           size = 0;       }              @Override      public int length() {           return size;       }              @Override      public boolean push(T data) {           Node node = new Node();           node.data = data;           node.pre = top;           // 改变栈顶指针           top = node;           size++;           return true;       }              @Override      public T pop() {           if (top != null) {               Node node = top;               // 改变栈顶指针               top = top.pre;               size--;               return node.data;           }           return null;       }              /**       * 将数据封装成结点       */      private final class Node {           private Node pre;           private T data;       }   }  public class MyLinkedStack implements MyStack { /** * 栈顶指针 */ private Node top; /** * 栈的长度 */ private int size; public MyLinkedStack() { top = null; size = 0; } @Override public boolean isEmpty() { return size == 0; } @Override public void clear() { top = null; size = 0; } @Override public int length() { return size; } @Override public boolean push(T data) { Node node = new Node(); node.data = data; node.pre = top; // 改变栈顶指针 top = node; size++; return true; } @Override public T pop() { if (top != null) { Node node = top; // 改变栈顶指针 top = top.pre; size--; return node.data; } return null; } /** * 将数据封装成结点 */ private final class Node { private Node pre; private T data; } }

两种实现的比较, 主要比较数据入栈和出栈的速度:

Java代码  @Test  public void testSpeed() {       MyStack stack = new MyArrayStack();       int num = 10000000;       long start = System.currentTimeMillis();       for (int i = 0; i  stack = new MyArrayStack(); int num = 10000000; long start = System.currentTimeMillis(); for (int i = 0; i  myStack = new MyArrayStack();       Integer result = num;       while (true) {           // 将余数入栈           myStack.push(result % n);           result = result / n;           if (result == 0) {               break;           }       }       StringBuilder sb = new StringBuilder();       // 按出栈的顺序倒序排列即可       while ((result = myStack.pop()) != null) {           sb.append(result);       }       return sb.toString();   }  private String conversion(int num, int n) { MyStack myStack = new MyArrayStack(); Integer result = num; while (true) { // 将余数入栈 myStack.push(result % n); result = result / n; if (result == 0) { break; } } StringBuilder sb = new StringBuilder(); // 按出栈的顺序倒序排列即可 while ((result = myStack.pop()) != null) { sb.append(result); } return sb.toString(); }

2. 检验符号是否匹配. '['和']', '('和')'成对出现时字符串合法. 例如"[][]()", "[[([]([])()[])]]"是合法的; "([(])", "[())"是不合法的.

遍历字符串的每一个char, 将char与栈顶元素比较. 如果char和栈顶元素配对, 则char不入栈, 否则将char入栈. 当遍历完成时栈为空说明字符串是合法的.

public boolean isMatch(String str) {       MyStack myStack = new MyArrayStack();       char[] arr = str.toCharArray();       for (char c : arr) {           Character temp = myStack.pop();           // 栈为空时只将c入栈           if (temp == null) {               myStack.push(c);           }           // 配对时c不入栈           else if (temp == '[' && c == ']') {           }            // 配对时c不入栈           else if (temp == '(' && c == ')') {           }            // 不配对时c入栈           else {               myStack.push(temp);               myStack.push(c);           }       }       return myStack.isEmpty();   }  public boolean isMatch(String str) { MyStack myStack = new MyArrayStack(); char[] arr = str.toCharArray(); for (char c : arr) { Character temp = myStack.pop(); // 栈为空时只将c入栈 if (temp == null) { myStack.push(c); } // 配对时c不入栈 else if (temp == '[' && c == ']') { } // 配对时c不入栈 else if (temp == '(' && c == ')') { } // 不配对时c入栈 else { myStack.push(temp); myStack.push(c); } } return myStack.isEmpty(); }

3. 行编辑: 输入行中字符'#'表示退格, '@'表示之前的输入全都无效.

使用栈保存输入的字符, 如果遇到'#'就将栈顶出栈, 如果遇到@就清空栈. 输入完成时将栈中所有字符出栈后反转就是输入的结果: 

 private String lineEdit(String input) {       MyStack myStack = new MyArrayStack();       char[] arr = input.toCharArray();       for (char c : arr) {           if (c == '#') {               myStack.pop();           } else if (c == '@') {               myStack.clear();           } else {               myStack.push(c);           }       }              StringBuilder sb = new StringBuilder();       Character temp = null;       while ((temp = myStack.pop()) != null) {           sb.append(temp);       }       // 反转字符串       sb.reverse();       return sb.toString();   }  

转载出处：http://coolxing.iteye.com/blog/1468674

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