一、顺序表的概念及结构

线性表（linear list）是n个具有相同特性的数据元素的有限序列。 线性表是⼀种在实际中广泛使用的数据结构，常见的线性表：顺序表、链表、栈、队列、字符串… 线性表在逻辑上是线性结构，也就说是连续的一条直线。但是在物理结构上并不一定是连续的，线性表在物理上存储时，通常以数组和链式结构的形式存储。

二、顺序表分类

顺序表和数组的区别

顺序表的底层结构是数组，对数组的封装，实现了常用的增删改查等接口。

顺序表分类

静态顺序表

概念：使用定长数组存储元素

#define N 10					// 长度恒定typedef int SeqListDataType;typedef struct SeqList
{SeqListDataType arr[N];		// 长度恒定int size;
} SeqList, *pSeqList;

静态顺序表缺陷：空间给少了不够用，给多了造成空间浪费。

动态顺序表

概念：按需申请，避免空间进一步浪费

typedef int SeqListDataType;typedef struct SeqList
{SeqListDataType* arr;		// 指针int size;					// 当前容量int capacity;				// 总容量
} SeqList, * pSeqList;

三、动态顺序表的实现(使用VS2022)

这里以实现动态顺序表为例，开发工具为VS2022。

动态顺序表常用的增删改查等接口包括：

1.初始化、销毁、打印内容

2.检查扩容

3.尾部插入、尾部删除、头部插入、头部删除

4.指定插入、指定删除、查找

在 SeqList.h 中：

#pragma once#include <stdio.h>
#include <assert.h>
#include <stdlib.h>// 初始化容量
#define INIT_CAPACITY 4// 扩容倍率
#define EXPANSION_MULTIPLE 2typedef int SeqListDataType;typedef struct SeqList
{SeqListDataType* arr;int size;int capacity;
} SeqList, * pSeqList;// 初始化、销毁、打印
void SeqListInit(pSeqList ps);void SeqListDestroy(pSeqList ps);void SeqListPrint(pSeqList ps);// 检查扩容
void CheckCapacity(pSeqList ps);// 尾插尾删、头插头删
void SeqListPushBack(pSeqList ps, SeqListDataType x);void SeqListPopBack(pSeqList ps);void SeqListPushFront(pSeqList ps, SeqListDataType x);void SeqListPopFront(pSeqList ps);// 插入、删除、查找
void SeqListInsert(pSeqList ps, int pos, SeqListDataType x);void SeqListErase(pSeqList ps, int pos);int SeqListFind(pSeqList ps, SeqListDataType x);

在 SeqList.c 中：

1.初始化、销毁、打印内容

#include "SeqList.h"// 初始化、销毁、打印
void SeqListInit(pSeqList ps)
{assert(ps);			// 防止进入空指针ps->arr = NULL;ps->size = 0;ps->capacity = 0;
}void SeqListDestroy(pSeqList ps)
{assert(ps);free(ps->arr);ps->size = 0;ps->capacity = 0;
}void SeqListPrint(pSeqList ps)
{assert(ps);for (int i = 0; i < ps->size; ++i){printf("%d ", ps->arr[i]);}printf("\n");
}

2.检查扩容

// 检查扩容
void CheckCapacity(pSeqList ps)
{assert(ps);if (ps->size == ps->capacity){int newCapacity = ps->capacity == 0 ? INIT_CAPACITY : ps->capacity * EXPANSION_MULTIPLE;// ps->arr 为空时，realloc 会转为 mallocSeqListDataType* temp = (SeqListDataType*)realloc(ps->arr, newCapacity * sizeof(SeqListDataType));if (temp == NULL){perror("realloc failed");return;}// 更新ps->arr = temp;ps->capacity = newCapacity;}
}

3.尾部插入、尾部删除、头部插入、头部删除

尾部插入

void SeqListPushBack(pSeqList ps, SeqListDataType x)
{assert(ps);					CheckCapacity(ps);			// 检查容量，不足扩容ps->arr[ps->size++] = x;	// 尾插
}

尾部删除

void SeqListPopBack(pSeqList ps)
{assert(ps);assert(ps->size > 0);	// 防止为空--ps->size;				// 直接--忽略掉当前位置
}

头部插入

void SeqListPushFront(pSeqList ps, SeqListDataType x)
{assert(ps);CheckCapacity(ps);for (int end = ps->size; end > 0; --end){ps->arr[end] = ps->arr[end - 1];}ps->arr[0] = x;++ps->size;
}

头部删除

void SeqListPopFront(pSeqList ps)
{assert(ps);assert(ps->size > 0);for (int begin = 0; begin < ps->size - 1; ++begin){ps->arr[begin] = ps->arr[begin + 1];}--ps->size;
}

4.指定插入、指定删除、查找

指定插入

void SeqListInsert(pSeqList ps, int pos, SeqListDataType x)
{assert(ps);assert(0 <= pos && pos <= ps->size); // 当 pos == ps->size 可以实现尾插 CheckCapacity(ps);for (int end = ps->size; end > pos; --end){ps->arr[end] = ps->arr[end - 1];}ps->arr[pos] = x;++ps->size;
}

指定插入与头部插入同理，只需将结束位置改为 pos 指定的位置。

指定删除

void SeqListErase(pSeqList ps, int pos)
{assert(ps);assert(ps->size > 0);assert(0 <= pos && pos < ps->size);	// 尾删不可删 pos == ps->size 位置上的for (int begin = pos; begin < ps->size - 1; ++begin){ps->arr[begin] = ps->arr[begin + 1];}--ps->size;
}

指定删除与头部删除同理，只需将开始位置改为 pos 指定的位置。

查找

int SeqListFind(pSeqList ps, SeqListDataType x)
{assert(ps);assert(ps->size > 0);// 找到返回下标，反之返回 -1for (int i = 0; i < ps->size; ++i){if (ps->arr[i] == x){return i;}}return -1;
}

四、代码优化

指定插入 包含 尾插头插，指定删除 包含 尾删头删。可以复用两者，提高代码复用率。

// 尾插尾删、头插头删
void SeqListPushBack(pSeqList ps, SeqListDataType x)
{SeqListInsert(ps, ps->size, x);
}void SeqListPopBack(pSeqList ps)
{SeqListErase(ps, ps->size - 1);
}void SeqListPushFront(pSeqList ps, SeqListDataType x)
{SeqListInsert(ps, 0, x);
}void SeqListPopFront(pSeqList ps)
{SeqListErase(ps, 0);
}

五、完整 SeqList.c 代码

#include "SeqList.h"// 初始化、销毁、打印
void SeqListInit(pSeqList ps)
{assert(ps);ps->arr = NULL;ps->size = 0;ps->capacity = 0;
}void SeqListDestroy(pSeqList ps)
{assert(ps);free(ps->arr);ps->size = 0;ps->capacity = 0;
}void SeqListPrint(pSeqList ps)
{assert(ps);for (int i = 0; i < ps->size; ++i){printf("%d ", ps->arr[i]);}printf("\n");
}// 检查扩容
void CheckCapacity(pSeqList ps)
{assert(ps);if (ps->size == ps->capacity){int newCapacity = ps->capacity == 0 ? INIT_CAPACITY : ps->capacity * EXPANSION_MULTIPLE;// ps->arr 为空时，realloc 会转为 mallocSeqListDataType* temp = (SeqListDataType*)realloc(ps->arr, newCapacity * sizeof(SeqListDataType));if (temp == NULL){perror("realloc failed");return;}// 更新ps->arr = temp;ps->capacity = newCapacity;}
}// 尾插尾删、头插头删
void SeqListPushBack(pSeqList ps, SeqListDataType x)
{SeqListInsert(ps, ps->size, x);
}void SeqListPopBack(pSeqList ps)
{SeqListErase(ps, ps->size - 1);
}void SeqListPushFront(pSeqList ps, SeqListDataType x)
{SeqListInsert(ps, 0, x);
}void SeqListPopFront(pSeqList ps)
{SeqListErase(ps, 0);
}// 插入、删除、查找
void SeqListInsert(pSeqList ps, int pos, SeqListDataType x)
{assert(ps);assert(0 <= pos && pos <= ps->size);CheckCapacity(ps);for (int end = ps->size; end > pos; --end){ps->arr[end] = ps->arr[end - 1];}ps->arr[pos] = x;++ps->size;
}void SeqListErase(pSeqList ps, int pos)
{assert(ps);assert(ps->size > 0);assert(0 <= pos && pos < ps->size);for (int begin = pos; begin < ps->size - 1; ++begin){ps->arr[begin] = ps->arr[begin + 1];}--ps->size;
}int SeqListFind(pSeqList ps, SeqListDataType x)
{assert(ps);assert(ps->size > 0);for (int i = 0; i < ps->size; ++i){if (ps->arr[i] == x){return i;}}return -1;
}