采用堆分配存储表示的串被称为堆串，与顺序串相比，地址空间仍是连续，但空间是在程序执行时动态分配的。

程序中会使用到的realloc函数：

//realloc ： （void *）reelloc (void *ptr,unsigned newsize);
//使用 ： char *str;
// str = (char *)realloc(str,20);

代码实现如下：

<span style="font-size:18px;">#pragma once

#include<iostream>

using namespace std;

#define MAX_SZIE 30

typedef struct
{
	char *str;
	int length;
}HeapString;

/*判断空*/
bool IsEmpty(HeapString *s);

/*初始化*/
void InintString(HeapString *s);

/*求长度*/
int Length(HeapString *s);

/*用字符串给串赋值*/
bool StrAssign(HeapString *s,char cstr[]);

/*打印*/
void StrPrint(HeapString *s);

/*在S的pos位置插入串T*/
bool StrInsert(HeapString *S,int pos,HeapString *T);

/*在S的pos位置删除长度为len的子串*/
bool StrDelete(HeapString *S,int len);

/*清空串*/
void ClearString(HeapString *s);

/*摧毁*/
void Destroy(HeapString *s);

/*从S的pos位置截取长为len的子串sub*/
bool SubString(HeapString *sub,HeapString *s,int len);

/*拼接*/
bool StringConcat(HeapString *T,HeapString *S,HeapString *S2);

 /*拷贝*/
bool StrCopy(HeapString *T,HeapString *S);

/*比较*/
int StrCompare(HeapString *T,HeapString *S);

/*从S的pos位置开始定位子串T的初始位置*/
int  StrIndex(HeapString *S,HeapString *T);

/*将S中的子串T全部用V替换*/
bool StrReplace(HeapString *S,HeapString *T,HeapString *V);</span>

<span style="font-size:18px;">#include "string.h"

/*堆串*/

void InintString(HeapString *s)
{
	s->length = 0;
	s->str = '\0';
}


bool IsEmpty(HeapString *s)
{
	return s->length == 0;
}


int Length(HeapString *s)
{
	return s->length;
}


void PrintString(char T[])
{
	cout << T << endl;
}

 
bool StrAssign(HeapString *s,char cstr[])
{
	int i = 0;
	int len = 0;

	if (s->str)
		free(s->str);

	for (i = 0; cstr[i] != '\0'; i++);
	len = i;

	if (!i)
	{
		s->str = '\0';
		s->length = 0;
	}
	else
	{
		s->str = (char *)malloc(sizeof(char)*len);
		if (s->str == NULL)
			return false;
		for (i = 0; i < len; i++)
		{
			s->str[i] = cstr[i];
		}
		s->length = len;
	}

		s->str[i] = cstr[i];
	
	s->length = i;
}


void StrPrint(HeapString *S)
{
	int i = 0;
	for (i = 0; i < S->length; i++)
	{
		cout <<S->str[i];
	}
	cout << endl;
}


void ClearString(HeapString *s)
{
	if (s->str)
		free(s->str);
	s->str = '\0';
	s->length = 0;
}


void Destroy(HeapString *s)
{
	if (s->str)
		free(s->str);
	s->str == NULL;
}


bool SubString(HeapString *sub,int len)
{
	if (sub->str)
		free(sub->str);

	if (pos < 0 || pos > s->length || len <= 0 || len > s->length - pos + 1)
		return false;

	sub->str = (char *)malloc(sizeof(char)*len);
	if (sub->str == NULL)
		return false;
	int i = 0;
	for (; i < len; i++)
	{
		sub->str[i] = s->str[i + pos - 1];
	}
	sub->str[len] = '\0';
	sub->length = len;
	
}


bool StringConcat(HeapString *T,HeapString *S1,HeapString *S2)
{
	T->str = (char *)realloc(T->str,sizeof(char)*(S1->length + S2->length));
	if (T->str == NULL)
		return false;

	int i = 0;
	for (; i < S1->length; i++)
	{
		T->str[i] = S1->str[i];
	}

	for (i = 0; i < S2->length; i++)
	{
		T->str[S1->length + i] = S2->str[i];
	}
	T->str[S1->length + S2->length] == '\0';
	T->length = S1->length + S2->length;

	return true;
}


bool StrCopy(HeapString *T,HeapString *S)
{
	if (S->str == '\0')
		return false;

	T->str = (char *)realloc(T->str,sizeof(char)*(S->length));
	if (T->str == NULL)
		return false;

	for (int i = 0; i < S->length; i++)
		T->str[i] = S->str[i];
	
	T->length = S->length;

	return true;
}


int StrCompare(HeapString *T,HeapString *S)
{
	int i = 0;
	for (; i < T->length && i < T->length; i++)
	{
		if (T->str[i] != S->str[i])
		{
			if (T->str[i] > S->str[i])
				return 1;
			return -1;
		}
	}

	if (T->length > T->length)
		return 1;
	else if (T->length < T->length)
		return -1;
	return 0;
}


bool StrDelete(HeapString *S,int len)
{
	int i = 0;
	char *p;
	if (pos<0 || pos > S->length || len < 0 || len > S->length - pos + 1)
		return false;

	p = (char*)malloc(S->length - len);
	if (p == NULL)
		return false; 

	for (i = 0; i <pos - 1; i++)
	{
		p[i] = S->str[i];
	}

	for (i = pos - 1; i < S->length - len; i++)
	{
		p[i] = S->str[i+len];
	}
	S->length = S->length - len;

	S->str = p;

	return true;
}


int StrIndex(HeapString *S,HeapString *T)
{
	if (pos < 0 || pos > S->length || IsEmpty(T))
		return 0;

	int i = pos - 1;
	int j = 0;

	while (i < S->length && j < T->length )
	{
		if (S->str[i] == T->str[j])
		{
			i++;
			j++;
		}
		else
		{
			i = i - j + 1;
			j = 0;
		}
	}
	if (j >= T->length)
		return i - j + 1;
	else
		return -1;
}


bool StrInsert(HeapString *S,HeapString *T)
{
	int i = 0;
	int s_len = S->length;
	int t_len = T->length;

	if (pos < 0 || pos - 1 >= S->length)
		return false;

	S->str = (char *)realloc(S->str,(S->length + T->length)*sizeof(char));
	if (S->str == NULL)
	{
		cout << "内存分配失败" << endl;
		return false;
	}
		
	for (i = S->length - 1; i >= pos - 1; i--)
	{
		S->str[i + T->length ] = S->str[i];
	}

	for (i = 0; i<T->length; i++)
	{
		S->str[pos - 1 + i] = T->str[i];
	}
	S->length += T->length;
	//S[i] = '\0';
	return true;
}


bool StrReplace(HeapString *S,HeapString *V)
{
	int i = 1;
	int flag;
	if (IsEmpty(T))
		return false;
	do
	{
		i = StrIndex(S,i,T);
		if (i)
		{
			StrDelete(S,Length(T));
			int flag = StrInsert(S,V);
			if (!flag)
				return false;

			i += Length(V);
		}
	} while (i);
	return true;
}</span>

<span style="font-size:18px;">#include "string.h"


void main()
{
	HeapString s1,s2,sub,T;
	char ch[MAX_SZIE+1];
	char a[] = "abcdefdeg";
	char b[] = "de";
	char c[] = "XY";

	InintString(&s1);
	//cout <<"请输入第1个串:"<< endl;
	//gets_s(ch);
	//StrAssign(&s1,ch);
	StrAssign(&s1,a);
	cout << "输出串s1: " << endl;
	StrPrint(&s1);

	
	//SubString(&sub,s1,2,3);
	//StrPrint(&sub);

	
	InintString(&s2);
	//cout << "请输入第2个串:" << endl;
	//gets_s(ch);
	StrAssign(&s2,b);
	cout << "输出串s2: " << endl;
	StrPrint(&s2);

	cout << endl;
	//InintString(&T);
	//StringConcat(&T,&s1,&s2);
	//StrPrint(&T);
	
	//StrCopy(&s1,&s2);
	//StrPrint(&s1);

	//cout << StrCompare(&s1,&s2) <<endl;
	
	//StrDelete(&s1,3);
	
	cout<<StrIndex(&s1,&s2)<<endl;


	InintString(&sub);
	StrAssign(&sub,c);
	StrPrint(&sub);

	StrReplace(&s1,&s2,&sub);
	//StrInsert(&s1,&sub);
	StrPrint(&s1);

	getchar();
}</span>