数据结构那些事儿(二)

说明：

这是转载的。

前一篇见：

http://blog.csdn.net/kakaxi_77/article/details/8333009

题目：数组中有重复数据，求出每个数据出现的次数并按照次数的由大到小排列出来

题目还是老题目，曲不离口，拳不离手，卖油翁2015：

1.二维数组

/*** Program Name：* Description： 数组中有重复数据，求出每个数据出现的次数并按照次数的由大到小排列出来* Methods：* @version ver：1.0*/public class CharCntTwo {private static int[][] iArray = {};public void handle(int[] arr){this.initArray(arr);this.sortArray();this.display();}public void initArray(int[] arr){if(null == arr || arr.length == 0)return;/*iArray = new int[arr.length][2];int i = 0;int key = 0;for(int iVar : arr){key = i++;iArray[key][0] = iVar;iArray[key][1] = 1;}*/int length = 0;Map map = new HashMap();for(int iVar : arr){map.put(iVar,"0");}iArray = new int[map.size()][2];System.out.println(iArray.length);System.out.println("=========");int index = 0;List list = new ArrayList();for(int i=0; i < arr.length; i++){int cnt = 1;if(list.contains(arr[i]))continue;for(int j=i+1; j < arr.length; j++){if(arr[i] == arr[j]){cnt++;continue;}}list.add(arr[i]);int key = index;System.out.println("key--->" + key);System.out.println("i--->" + i);iArray[key][0] = arr[i];iArray[key][1] = cnt;index++;}}public void sortArray(){for(int i=0; i<iArray.length -1; i++){for(int j=0; j<iArray.length -1 - i; j++){if(iArray[j][1] > iArray[j+1][1]){int[] temp = iArray[j];iArray[j] = iArray[j+1];iArray[j+1] = temp;}}}}public void display(){for(int i=0; i<iArray.length; i++){System.out.println(iArray[i][1] + "--->" + iArray[i][0]);}}}

评论：

重点是学会二维数组的用法！

2. 链表

Node类

public class Node {public int data;public String desc;public Node next;public Node(int data, String desc){this.data = data;this.desc = desc;}public void displayNode(){System.out.println(this.data + " --> " + this.desc);}}

链表类：

public class LinkList {private Node first;private LinkList(){first = null;}public boolean isEmpty(){return null == first ? true : false;}public void insertFirst(int key, String str){Node newNode = new Node(key, str);if(null == first){first = newNode;}else{newNode.next = first;first = newNode;}}public Node deletefirst(){if(isEmpty())return null;Node temp = first;first = first.next;return temp;}public Node find(int key){if(this.isEmpty())return null;Node current = first;while(current.data != key){if(null == current.next){return null;}else{current = current.next;}}return current;}public Node delete(int key){if(this.isEmpty())return null;Node current = first;Node previous = first;while(current.data != key){if(null == current.next){return null;}else{previous = current;current = current.next;}}if(first == current){first = first.next;}else{previous.next = current.next;}return current;}public void displayLink(){if(this.isEmpty())return;Node current = first;while(null != current){current.displayNode();current = current.next;}}public static void main(String[] args){LinkList list = new LinkList();;list.insertFirst(1, "a");list.insertFirst(2, "b");list.insertFirst(3, "c");list.displayLink();System.out.println("==========1=========");Node node = list.find(3);node.displayNode();System.out.println("==========2=========");list.delete(2);list.displayLink();}}

评论：

普通链表，头插法。

3. 用链表实现的队列：

Node类

public class Node {public int data;public String value;public Node next;public Node(int data, String value){this.data = data;this.value = value;}public void display(){System.out.println(this.data + " -- > " + this.value);}}

队列实现：

/** * Program Name：* Description：* Methods：* @version ver：1.0** Modified No：* Modified By：* Modified Date：* Modified Description:* 用双端链表实现的队列 * 2015-05-03 */public class LinkQueue {private Node first;private Node last;private LinkQueue(){this.first = null;this.last = null;}public boolean isEmpty(){return null == first ? true : false;}/** * 从尾部插入 * @param key * @param val */public void insertLast(int key, String val){Node newNode = new Node(key, val);if(this.isEmpty()){first = newNode;last = newNode;}else{last.next = newNode;last = newNode;}}/** * 从头部移除 * @return */public Node remove(){if(this.isEmpty())return null;Node temp = first;first = first.next;return temp;}public void display(){Node current = first;while(null != current){current.display();current = current.next;}}public static void main(String[] args){LinkQueue queue = new LinkQueue();queue.insertLast(1, "a");queue.insertLast(2, "b");queue.insertLast(3, "c");System.out.println("===========1===========");queue.display();System.out.println("===========2===========");Node temp = queue.remove();temp.display();System.out.println("===========3===========");queue.display();}}

评论:

Java 自带队列类，参见LinkedList

4.树

节点类

public class Node {public int data;public String desc;public Node leftChild;public Node rightChild;public boolean isValid;public Node(int data, String str){this.data = data;this.desc = str;isValid = true;}public String toString(){return this.data + "-->" + this.desc;}}

树类：

public class Tree {public Node root;public Node find(int key){Node current;if(null == root)return null;current = root;while(null != current){if(key == current.data)break;if(key < current.data){current = current.leftChild;}else{current = current.rightChild;}}return (null == current) ? null : current;}public void insert(int key, String value){Node node = new Node(key, value);Node current;Node parent;boolean isLeftChild = false;if(null == root){root = node;return;}current = root;parent = root;while(null != current){parent = current;if(key < current.data){current = current.leftChild;isLeftChild = true;}else{current = current.rightChild;isLeftChild = false;}}if(isLeftChild){parent.leftChild = node;}else{parent.rightChild = node;}}/** * 中序遍历 * @param node */public void inOrder(Node node){if(null != node){inOrder(node.leftChild);if(node.isValid)System.out.println(node.toString());inOrder(node.rightChild);}}public boolean delete(int key){Node current;if(null == root)return false;current = root;while(null != current){if(key == current.data)break;if(key < current.data){current = current.leftChild;}else{current = current.rightChild;}}if(null == current)return false;current.isValid = false;   //置标志位，表示删除return true;}}

评论：

一颗普通的树，删除的用法很灵活。

实际中，Java中自带红黑树：TreeMap

【总结】

实战中要灵活运用数据结构！

重点：不要重复发明轮子！

                                                ----2015-05-03