剑指offer面试题 java解答26-30

面试题26:复杂链表的复制

import java.util.HashMap;public class Test26{    private class Node<T>{        T valueT=null;        Node next=null;        Node sibling=null;        public Node(T valueT) {            this.valueT = valueT;        }    }    private Node head=null;    public Node getHeadNode(){        return head;    }    public <T> Node insertTail(T value){        Node nextNode=null;        if (head==null) {            head=new Node(value);            return head;        }else {            nextNode=head;            while (nextNode.next!=null)             {                nextNode=nextNode.next;            }            nextNode.next=new Node(value);            return nextNode.next;        }    }    private Node ReconnectNodes(Node head) {        Node nowNode=head;        Node cloneNodeHead=null;        Node cloneNode=null;        if (head!=null) {            cloneNodeHead=nowNode.next;            cloneNode=cloneNodeHead;            nowNode=cloneNodeHead.next;            while (nowNode!=null) {                cloneNode.next=nowNode.next;                cloneNode=nowNode.next;                nowNode=cloneNode.next;            }        }        return cloneNodeHead;    }    private void ConnectSiblingNodes(Node head) {        if (head!=null) {            Node nowNode=head;            while (nowNode!=null) {                Node nowCloneNode=nowNode.next;                if (nowNode.sibling!=null) {                    nowCloneNode.sibling=nowNode.sibling.next;                }                nowNode=nowCloneNode.next;            }        }           }    private void CloneNodes(Node head) {        if (head!=null) {            Node nowNode=head;            while (nowNode.next!=null) {                Node cloneNode=new Node(nowNode.valueT);                Node nextNode=nowNode.next;                nowNode.next=cloneNode;                cloneNode.next=nextNode;                nowNode=nextNode;            }            Node cloneNode=new Node(nowNode.valueT);            nowNode.next=cloneNode;        }    }    public Node Clone(Node head){        CloneNodes(head);        ConnectSiblingNodes(head);        return ReconnectNodes(head);    }    public static void main(String[] args) {        HashMap<Character, Object> map=new HashMap<Character, Object>();        Object[] a={'A','B','C','D','E'};        Test26 t=new Test26();        for (int i = 0; i < a.length; i++) {            Node node=t.insertTail(a[i]);            map.put((Character) a[i], node);        }        ((Node)(map.get('A'))).sibling=((Node)(map.get('C')));        ((Node)(map.get('B'))).sibling=((Node)(map.get('E')));        ((Node)(map.get('D'))).sibling=((Node)(map.get('B')));        Node cloneHead=t.Clone(t.getHeadNode());        if (cloneHead!=null)         {            while (cloneHead!=null)             {                System.out.print(cloneHead.valueT);                if (cloneHead.sibling!=null)                 {                    System.out.println(cloneHead.sibling.valueT);                }else {                    System.out.println();                }                cloneHead=cloneHead.next;            }                   }    }}

面试题27:二叉搜索树与双向链表

public class Test27{    private class Node<T> {        public T value;        public Node<T> lChild;        public Node<T> rChild;        public Node(T value) {            this.value = value;        }    }    public Node root=null;    private int pos = 0;    public <T> void creatBiTree(T[] value){        pos=0;        root=creatBiTree(root, value);    }    // 以node为根节点，创建一棵树，返回此根节点    private <T> Node creatBiTree(Node node, T[] value) {        T t = value[pos];        pos++;        if (t == null) {            return null;        } else {            node = new Node<T>(t);            node.lChild = creatBiTree(node.lChild, value);            node.rChild = creatBiTree(node.rChild, value);        }        return node;    }    public Node Convert(Node root){        Node lastNode=null;        Node tailNode=ConvertNode(root, lastNode);        Node head=tailNode;        while (head.lChild!=null) {            head=head.lChild;        }        return head;    }    private Node ConvertNode(Node nowNode,Node lastNode){        if (nowNode==null)        {            return null;        }        if (nowNode.lChild!=null)        {            lastNode=ConvertNode(nowNode.lChild, lastNode);        }        nowNode.lChild=lastNode;        if (lastNode!=null)        {            lastNode.rChild=nowNode;        }        lastNode=nowNode;        if (nowNode.rChild!=null) {            lastNode=ConvertNode(nowNode.rChild, lastNode);        }        return lastNode;    }    public static void main(String[] args) {        Object[] a = { 10, 6, 4, null, null, 8, null, null, 14, 12, null, null, 16, null, null };        Test27 t = new Test27();        t.creatBiTree(a);        Node head=t.Convert(t.root);        while (head!=null) {            System.out.println(head.value);            head=head.rChild;        }    }}

面试题28:字符串的排列

public class Test28 {    public void Permutation(String str){        permutation(str, 0);    }    //第i个字符和后面的全排列交换    private static void permutation(String s, int i) {          char[] str=s.toCharArray();        if (i>s.length()) {            return ;        }else if (i==s.length()) {            System.out.println(String.valueOf(str));        }else {            for (int j = i; j < str.length; j++) {                char tmp=str[j];                str[j]=str[i];                str[i]=tmp;                permutation(String.valueOf(str), i+1);            }        }    }    public static void main(String[] args) {        Test28 t=new Test28();        String str="abcd";        t.Permutation(str);    }}

面试题29:数组中出现次数超过一半的数字

public class Test29 {    public int MoreThanHalfNum(int[] numbers) throws Exception{        if (numbers==null) {            throw new Exception("invalid input");        }        int number=numbers[0];        int times=1;        for (int i = 1; i < numbers.length; i++) {            if (numbers[i]!=number) {                if (--times==0) {                    number=numbers[i];                    times=1;                }            }else {                times++;            }        }        int sum=0;        for (int i = 0; i < numbers.length; i++)         {            if (numbers[i]==number)             {                sum++;            }        }        if (sum>numbers.length/2) {            return number;        }else {            throw new Exception("without");        }           }    public static void main(String[] args) throws Exception {        int[] numbers={1,2,3,2,2,2,5,4,2};        Test29 t=new Test29();        int number=t.MoreThanHalfNum(numbers);        System.out.println(number);    }}

面试题30:最小的K个数

public class Test30 {    private static int leftChild(int i)    {        return 2*i+1;    }    //下滤实现大顶堆    public static <T extends Comparable<? super T>> void percolateDownSort(T[] a,int i,int n)    {        int child;        T tmp;        for (tmp=a[i];leftChild(i)<n;i=child)         {            child=leftChild(i);            if (child<n-1&&a[child].compareTo(a[child+1])<0)            {                child++;            }            if (tmp.compareTo(a[child])<0)             {                a[i]=a[child];            }else {                break;            }        }        a[i]=tmp;    }    public static <T extends Comparable<? super T>> T returnMax(T[] a)    {        int length=a.length;        percolateDownSort(a, 0, length);        return a[0];    }    public Integer[] getLeastNumbers(int k,Integer[] a) throws Exception{        if (a==null||k<0||k>a.length) {            throw new Exception("invalid input");        }        Integer[] result=new Integer[k];        System.arraycopy(a, 0, result, 0, k);        if (a.length<k)         {            return result;        }else {            for (int i = k; i < a.length; i++)             {                Integer max=returnMax(result);                if (max>a[i])                 {                    result[0]=a[i];                }            }        }        return result;    }    public static void main(String[] args) throws Exception {        Integer[] a={4,6,1,2,8,3,0,9,7,5};        Test30 t=new Test30();        Integer[] result=t.getLeastNumbers(4, a);        for (int i = 0; i < result.length; i++) {            System.out.println(result[i]);        }    }}