算法.链表反转

链表反转的思路：

 

lrs.h:

/*************************************************************************
        > File Name: lrs.h
        > Author: zhoulin
        > Mail: 715169549@qq.com
        > Created Time: Sun 17 Apr 2016 01:08:11 PM CST
 ************************************************************************/

#ifndef _LRS_H
#define _LRS_H
typedef struct _listNode
{
    int v;
    struct _listNode *next;
}listNode;
//reverse a list node start with start,end whith end postion
listNode *listReverse(listNode *p,int start,int end);
#endif

lrs.c:

/*************************************************************************
        > File Name: lrs.c
        > Author: zhoulin
        > Mail: 715169549@qq.com
        > Created Time: Sun 17 Apr 2016 01:09:37 PM CST
 ************************************************************************/
#include "lrs.h"
#include <stdio.h>
void listPrt(listNode *p)
{
    while(p != NULL)
    {
        if(p->next == NULL)
        {
            fprintf(stdout,"%d\n",p->v);
            break;
        }
        fprintf(stdout,"%d ->",p->v);
        p = p->next;
    }
}
/*
 *采用分治法
 * 1.拆分链为2个链表，t_head保存目标链表的头节点，t_tail保存目标链表的最后一个节点
 * 2.cur遍历到t_tail的下一个节点，n_head为t_tail下一个节点开始的新链表，采用头插法把cur节点插入到新链表，依次循环
 * 3.t_tail的下一个节点为新链表的头节点，t_tail->next = n_head;最后把n_tail指向cur遍历的剩余节点。
 */
listNode *listReverse(listNode *p,int start,int end)
{
    if(start >= end)
    {
        return p;
    }
    listNode *t_head,*t_tail;//target_head为目标链表第一节点，target_cur为目标链表的最后一个节点
    listNode *cur,*n_head,*n_tail;//cur为遍历p的游标节点
    cur = n_head = n_tail =NULL;
    t_head = t_tail = NULL;
    int i = 1;
    for(;i <start;i++)
    {
        if(i == 1)
        {
            t_head = p;
        }
        if(i == start -1)
        {
            t_tail = p;
        }
        p = p->next;//find list head next node
    }
    cur = p;
    for(;(i <= end)&& (cur != NULL);i++)
    {
        listNode *pn = cur->next;
        if(n_head == NULL)
        {
            n_head = n_tail = cur;
        }else{
            cur->next = n_head;
            n_head = cur;
        }
        cur = pn;
    }
    if(t_head == NULL)
    {
        t_head = n_head;
        t_tail = n_tail;
    }else{
        t_tail->next = n_head;
    }
    if(n_tail != NULL)
        n_tail->next = cur;
    return t_head;
}
int main(void)
{
    int i,j;
    for(i = 6;i>=1;i--)
    {
        for(j=1;j<=i;j++)
        {
            if(j>=i)
            {
                continue;
            }
            listNode a1,a2,a3,a4,a5,a6;
            a1.v =1;
            a2.v =2;
            a3.v =3;
            a4.v =4;
            a5.v =5;
            a6.v =6;
            a1.next = &a2;
            a2.next = &a3;
            a3.next = &a4;
            a4.next = &a5;
            a5.next = &a6;
            a6.next = NULL;
            listNode *tmp = &a1;
            fprintf(stdout,"------------------------source list----------------------------\n");
            listPrt(tmp);
            fprintf(stdout,"------------------------listReverse(%d,%d)---------------------\n",j,i);
            listNode *rs = listReverse(tmp,j,i);
            if(rs != NULL)
                listPrt(rs);
                fprintf(stdout,"\n");
        }
    }
    return 0;
}

运行结果:

root@:/data/code/cwork/demo:./lrs
------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(1,6)---------------------
6 ->5 ->4 ->3 ->2 ->1

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(2,6)---------------------
1 ->6 ->5 ->4 ->3 ->2

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(3,6)---------------------
1 ->2 ->6 ->5 ->4 ->3

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(4,6)---------------------
1 ->2 ->3 ->6 ->5 ->4

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(5,6)---------------------
1 ->2 ->3 ->4 ->6 ->5

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(1,5)---------------------
5 ->4 ->3 ->2 ->1 ->6

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(2,5)---------------------
1 ->5 ->4 ->3 ->2 ->6

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(3,5)---------------------
1 ->2 ->5 ->4 ->3 ->6

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(4,5)---------------------
1 ->2 ->3 ->5 ->4 ->6

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(1,4)---------------------
4 ->3 ->2 ->1 ->5 ->6

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(2,4)---------------------
1 ->4 ->3 ->2 ->5 ->6

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(3,4)---------------------
1 ->2 ->4 ->3 ->5 ->6

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(1,3)---------------------
3 ->2 ->1 ->4 ->5 ->6

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(2,3)---------------------
1 ->3 ->2 ->4 ->5 ->6

------------------------source list----------------------------
1 ->2 ->3 ->4 ->5 ->6
------------------------listReverse(1,2)---------------------
2 ->1 ->3 ->4 ->5 ->6