寻找单链表中倒数第k个元素

来源：互联网发布：姚明生涯平均数据编辑：程序博客网时间：2024/05/22 07:53

原理：设置快慢指针，快指针和慢指针初始时都指向链表首节点，然后快指针向后走k个单位，再让慢指针和快指针同时向后走，当快指针的值为空时慢指针指向的节点的数据域即为所求。

算法:

#include<iostream>using namespace std;typedef int ElemType;typedef struct _NODE_//节点声明,头结点数据域存放链表长度{    ElemType data;    struct _NODE_ *next;}Node,*pNode,*List;void search(List,int,int&);//寻找倒数第k个元素void printList(List);int main(){    int size;    cin>>size;    ElemType data;    List list = (pNode)malloc(sizeof(Node));    if(!list)    {        return -1;    }    list->data = 0;    list->next = NULL;    for(int i = 0; i < size;i++)    {        cin>>data;        pNode pNew = (pNode)malloc(sizeof(Node));        if(!pNew)        {            return -1;        }        pNew->next = list->next;        pNew->data = data;        list->next = pNew;        list->data++;    }    cout<<"print list:";    printList(list);    int index,e;    cin>>index;    search(list,index,e);    cout<<"e = "<<e;    return 0;}/***    寻找倒数第index个元素，找到则将该元素的值赋给e，否则直接返回.*    1<=index<=list.size()***/void search(List list,int index,ElemType &e){    if(!list || index<0 || index>list->data)//参数判断        return;    pNode p,q;//设置快慢指针    p = q = list->next;    while(index-->0)    {        /*if(!q)        {            return;        }*/        q = q->next;     }    while(q)    {        p = p->next;        q = q->next;    }    e = p->data;}void printList(List list){    if(!list)    {        return;    }    pNode p = list->next;    while(p)    {        cout<<p->data<<" ";        p = p->next;    }    cout<<endl;}

测试：

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