本文主要是介绍嵌入式学习——数据结构(双向无头有环链表、内核链表、栈)——day48,希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!
1. 约瑟夫环问题——双向无头回环链表
1.1 问题描述
给定 ( n ) 个人(编号为 ( 1, 2, \ldots, n )),他们围成一个圈。从第一个人开始报数,每报到第 ( k ) 个人时,杀掉这个人,然后从下一个人重新开始报数。重复这个过程,直到所有人都被杀死。约瑟夫环问题是要确定最后一个幸存者的编号。
1.2 实质
每次删除循环链表中的一个节点,直到链表中仅剩一个节点结束
2. 双向无头循环链表代码
2.1 makefile
OBJ:=a.out
OBJS+=main.c doublelink.c
CCl=gcc$(OBJ):$(OBJS)$(CC) $^ -o $@
.PHONY:
clean:rm $(OBJ)
test:valgrind --tool=memcheck --leak-check=full ./$(OBJ)
2.2 double.h
#ifndef _DOUBLELINK_H_
#define _DOUBLELINK_H_typedef struct stu
{int id;char name[32];int score;
}DataType;typedef struct node
{DataType data;struct node *ppre;struct node *pnext;
}DouNode;typedef struct list
{DouNode *phead;int clen;
}DouList;extern DouList *create_dou_link();
extern int is_empty_dou_link(DouList *plist);
extern void dou_link_for_each(DouList *plist, int dir);
extern int push_head_dou_link(DouList *plist, DataType data);
extern int push_tail_dou_link(DouList *plist, DataType data);
extern int pop_head_dou_link(DouList *plist);
extern int pop_tail_dou_link(DouList *plist);
extern void loop_dou_link(DouList *plist);
extern DouNode *Joseph_loop(DouList *plist);
extern void dou_link_for_remain(DouList *plist);#endif
2.3 double.c
#include "doublelink.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>DouList *create_dou_link()//创建标签
{DouList *plist = NULL;plist = (DouList *)malloc(sizeof(DouList));if (NULL == plist){perror("fail to malloc");return NULL;}plist->phead = NULL;plist->clen = 0;return plist;
}int is_empty_dou_link(DouList *plist)//判断空链表
{if (NULL == plist->phead){return 1;}return 0;
}int push_head_dou_link(DouList *plist, DataType data)//头插
{DouNode *pnode = NULL;pnode = malloc(sizeof(DouNode));if (NULL == pnode){perror("fail to malloc");return -1;}pnode->data = data;pnode->ppre = NULL;pnode->pnext = NULL;if (is_empty_dou_link(plist))//空链表直接插{plist->phead = pnode;}else{pnode->pnext = plist->phead;plist->phead->ppre = pnode;plist->phead = pnode;}plist->clen++;return 0;
}int push_tail_dou_link(DouList *plist, DataType data)//头插
{DouNode *p = NULL;DouNode *pnode = NULL;pnode = malloc(sizeof(DouNode));if (NULL == pnode){perror("fail to malloc");return -1;}pnode->data = data;pnode->ppre = NULL;pnode->pnext = NULL;if (is_empty_dou_link(plist))//空链表直接插{plist->phead = pnode;}else{ p = plist->phead;while (p->pnext != NULL){p = p->pnext;}p->pnext = pnode;pnode->ppre = p;}plist->clen++;return 0;
}int pop_head_dou_link(DouList *plist)//头删
{if (is_empty_dou_link(plist))//空链表直接结束程序{return -1;}DouNode *pfree = NULL;pfree = plist->phead;plist->phead = pfree->pnext;//标签指向第二个节点首地址if (plist->phead != NULL)//判断是否空链表{plist->phead->ppre = NULL;//将第二个节点的ppre变为NULL}free(pfree);plist->clen--;return 0;
}int pop_tail_dou_link(DouList *plist)//尾删
{if (is_empty_dou_link(plist))//空链表程序结束{return -1;}DouNode *pfree = NULL;pfree = plist->phead;while (pfree->pnext)//指针指向最后一个节点{pfree = pfree->pnext;}if (pfree->ppre != NULL)//链表有两个以上节点{pfree->ppre->pnext = NULL;}else //链表只有一个节点{plist->phead = NULL;}free(pfree);plist->clen--;return 0;
}void loop_dou_link(DouList *plist)//将非回环链表改为双向回环链表
{DouNode *ptmpnode = NULL;ptmpnode = plist->phead;while (ptmpnode->pnext != NULL)//将指针移动到末尾节点{ptmpnode = ptmpnode->pnext;}ptmpnode->pnext = plist->phead;plist->phead->ppre = ptmpnode;
}void dou_link_for_remain(DouList *plist)//打印约瑟夫回环一次处理后链表中剩下的成员信息
{int i = 0;DouNode *ptmpnode = plist->phead;for (i = 0; i < plist->clen; i++){printf("%d ", ptmpnode->data.id);printf("%s ", ptmpnode->data.name);printf("%d\n", ptmpnode->data.score);ptmpnode = ptmpnode->pnext;}printf("=========================\n");
}DouNode *Joseph_loop(DouList *plist)//约瑟夫回环、实质是删除链表节点直到留下最后一个节点为止
{DouNode *pfreenode = NULL;//DouNode *ptmpnode = NULL;//指向回环ptmpnode = plist->phead;while (ptmpnode != ptmpnode->pnext)//判断回环是否只剩下一个节点{pfreenode = ptmpnode;//指向当前所在回环的位置pfreenode = pfreenode->pnext->pnext;//回环向后移动两个单位pfreenode->ppre->pnext = pfreenode->pnext;pfreenode->pnext->ppre = pfreenode->ppre; ptmpnode = pfreenode->pnext;//记录要删除的回环的下一个位置,保证循环的延续if (pfreenode == plist->phead)//判断要删除的节点是否是表头后的第一个节点、若是,给表头接入要删除节点的下一个节点{plist->phead = ptmpnode;}free(pfreenode);plist->clen--;dou_link_for_remain(plist);//打印链表中剩下的节点信息}return ptmpnode;
}
2.4 main.c
#include <stdio.h>
#include <stdlib.h>
#include "doublelink.h"int main(void)
{DataType stus[] = {{1, "doinb", 100},{2, "lwx", 67},{3, "lqs", 99},{4, "tian", 98},{5, "gimgoon", 78},{6, "xinyi", 88},{7, "nuguri", 99},{8, "khan", 77},{9, "bo", 94},{10, "xiaolaohu", 60}};DouNode *ptmpnode = NULL;int i = 0;DouList *plist = create_dou_link();//表头创建if (NULL == plist){return -1;}for (i = 0; i < sizeof(stus) / sizeof(stus[0]); i++)//给链表中插入结构体中的所有内容{push_tail_dou_link(plist, stus[i]);//尾插}dou_link_for_each(plist, 1);dou_link_for_each(plist, 0);loop_dou_link(plist);//创建双向回环链表ptmpnode = Joseph_loop(plist);//约瑟夫回环printf("%s\n", ptmpnode->data.name); return 0;
}
2.5 判断单向链表是否有环
利用快慢指针,慢指针走一步,快指针走两步
快指针每走一步,判断是否为空或者是否与慢指针相遇,相遇为有环链表
3. 内核链表(有头、双向循环链表)
3.1 定义
Linux内核链表是一种双向循环链表,它的实现非常简洁而高效,主要通过一些宏和内联函数来操作链表。链表节点的结构定义在头文件 <linux/list.h>
中。
3.1 offsetof宏
获取结构体某个成员到结构体开头的偏移量
3.2 container_of宏
通过offsetof偏移量获取结构体的首地址
3. 栈
3.1 定义
栈(Stack)是一种抽象的数据结构,它遵循后进先出(LIFO, Last In First Out)的原则。也就是说,最后放入栈中的元素最先被取出。
3.2 栈的基本操作
1. 入栈、压栈:将一个元素放入栈顶。
2. 出栈、弹栈:从栈顶移除一个元素。
3. 取栈顶元素:查看栈顶元素但不移除它。
4. 判断栈是否为空:检查栈中是否有元素。
3.3 分类
(1)按实现方式分类:栈分为顺序栈和链式栈
1. 顺序栈
使用数组实现的栈,数组中的元素按顺序存储。优点是实现简单,访问效率高;缺点是栈的容量固定,扩展不便。
2. 链式栈
使用链表实现的栈,链表的每个节点存储一个栈元素。优点是栈的容量可以动态扩展;缺点是指针操作复杂,访问效率相对较低。
(2)按用途来分类
1. 操作系统栈
用于管理程序执行时的函数调用,保存函数调用的返回地址、本地变量等信息。操作系统栈通常是顺序栈,采用固定大小。
1. 局部变量
2. 函数的形参、返回值
3. 函数调用关系——保护现场、恢复现场
3.4 数据结构中的栈——链式栈
4. 面试考点
区分满增栈、满减栈、空增栈、空减栈(前提:仅限于顺序栈,数组方式构成的)
4.1 满栈和空栈——判断栈顶所在位置是否存有数据而非整个栈有没有数据
1. 满栈:栈顶所在位置有数据
入栈操作流程:先向上移动栈顶指针,再将数据压入栈中
2. 空栈:栈顶所在位置没有数据
入栈操作流程:先将数据压入栈顶,再向上移动栈顶指针
4.2 增栈和减栈——判断栈的生长方向
0x1000与0x2000,内存高地址为0x2000,内存低地址为0x1000
1. 增栈:数据入栈时栈顶指针向内存高地址移动
2. 减栈:数据入栈时栈顶指针向内存低地址移动
(1) 满增栈
1. 出栈时:栈顶指针向内存高地址移动,再向栈顶入栈数据,
2. 出栈时:出栈数据,栈顶指针向内存低地址移动,
(2) 满减栈
(3) 空增栈
1. 出栈时:先向栈顶入栈数据,栈顶指针向内存高地址移动
2. 出栈时:栈顶指针向内存低地址移动,出栈数据
(4) 空减栈
5. 数据结构中的栈——链式栈
5.1 代码
(1)makefile
OBJ:=a.out
OBJS+=main.c stack.c
CCl=gcc$(OBJ):$(OBJS)$(CC) $^ -o $@
.PHONY:
clean:rm $(OBJ)
test:valgrind --tool=memcheck --leak-check=full ./$(OBJ)
注意:在终端输入make test可以测试销毁是否成功以及是否有内存泄漏
(2)stack.h
#ifndef _STACK_H_
#define _STACK_H_typedef int DataType;typedef struct stact_node
{DataType data;struct stact_node *pnext;
}StackNode;typedef struct Stack
{StackNode *ptop;int clen;
}StackList;extern StackList *create_stack();
extern int is_empty_stack(StackList *plist);
extern int push_stack(StackList *plist, DataType data);//入栈头插
extern void stack_for_each(StackList *plist);
extern int pop_stack(StackList *plist, DataType *pdata);//出栈头删
extern void clear_stack(StackList *plist);
extern void destory_stack(StackList *plist);
extern int get_stack_top(StackList *plist, DataType *pdata);#endif
(3)stack.c
#include <stdio.h>
#include <stdlib.h>
#include "stack.h"StackList *create_stack()
{StackList *plist = malloc(sizeof(StackList));if (NULL == plist){perror("fail to malloc");return NULL;}plist->ptop = NULL;plist->clen = 0;return plist;
}int is_empty_stack(StackList *plist)
{if (NULL == plist->ptop){return 1;}return 0;
}int push_stack(StackList *plist, DataType data)//入栈头插
{StackNode *pnode = malloc(sizeof(StackNode));if (NULL == pnode){perror("fail to malloc");return -1;}pnode->data = data;pnode->pnext = NULL;pnode->pnext = plist->ptop;plist->ptop = pnode;plist->clen++;return 0;
}void stack_for_each(StackList *plist)
{StackNode *ptmp = plist->ptop;while (ptmp != NULL){printf("%d ", ptmp->data);ptmp = ptmp->pnext;}printf("\n");
}int pop_stack(StackList *plist, DataType *pdata)//出栈头删
{if (is_empty_stack(plist)){return -1;}StackNode *pfree = plist->ptop;plist->ptop = pfree->pnext;if (pdata != NULL)//传入非空地址,将删除的节点的数据传出{*pdata = pfree->data;}free(pfree);plist->clen--;return 0;
}void clear_stack(StackList *plist)//清空栈区
{while (!is_empty_stack(plist)){pop_stack(plist, NULL);}
}void destory_stack(StackList *plist)
{if (!is_empty_stack(plist)){clear_stack(plist);}free(plist);
}int get_stack_top(StackList *plist, DataType *pdata)//获得栈顶数据
{if (is_empty_stack(plist)){return -1;}*pdata = plist->ptop->data;return 0;
}
(4)main.c
#include <stdio.h>
#include <stdlib.h>
#include "stack.h"int main(void)
{DataType tmpdata = 0;DataType data[] = {1, 2, 3, 4, 5};StackNode *ptmpnode = NULL;int i = 0;int ret = 0;StackList *plist = create_stack();//创建栈表头if (NULL == plist){return -1;}for (i = 0; i < sizeof(data) / sizeof(data[0]); i++)//入栈所有数据{push_stack(plist, data[i]);//入栈头插}stack_for_each(plist);//遍历打印所有数据#if 0for (i = 0; i < sizeof(data)/sizeof(data[0]); i++)//获取栈顶元素并打印,出栈数据,打印栈中的剩下元素{printf("======== %d ========", i);ret = get_stack_top(plist, &tmpdata);if (0 == ret){printf("ptop data:%d ", tmpdata);}pop_stack(plist, NULL);stack_for_each(plist);//遍历打印所有数据}
#endif#if 0clear_stack(plist);//清理栈中所有节点if (is_empty_stack(plist)){printf("clear_stack success!\n");}
#endif#if 1destory_stack(plist);
#endifreturn 0;
}
5.2 应用
1. 撤回操作
2. 浏览器返回上一层操作
3. 计算器
6.
中缀表达式
前缀表达式
后缀表达式
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