C语言数据结构串的表示与操作的实现

串的堆分配储存表示

typedef struct {
	char* ch;//若是非空字符串,则按串长分配存储区,否则ch为NULL
	int length;//串长度
} HString;

生成一个其值等于串常量的串

HString StrAssign(HString Str, char* chars) {
	//生成一个其值等于串常量的chars的串T
	if (Str.ch) {
		//释放T的空间
		free(Str.ch);
	}
	int len = 0;
	printf_s("chars=%s\n", chars);
	while (1) {
		len++;
		if (chars[len] == '\0') {
			//TODO
			break;
		}
	}
	if (!len) {
		//长度为0为ch赋NULL值
		Str.ch = NULL;
		Str.length = 0;
	}
	else {
		if (!(Str.ch = (char*)malloc(len * sizeof(char)))) {
			//空间不足退出
			exit(ERROR);
		}
		for (int i = 0; i <= len - 1; i++) {
			//TODO
			Str.ch[i] = chars[i];
		}
		Str.ch[len] = '\0';
		printf("Str.ch=%s\n", Str.ch);
		Str.length = len;
	}
	return Str;
}

比较字符串

int StrCompares(HString S, HString T) {
	//	若S>T,则返回值>0;若S<T,则返回值=0,若S<T,则返回值<0
	printf_s("123\n");
	for (int i = 0; i <= S.length && i < T.length; ++i) {
		//TODO
		if (S.ch[i] != T.ch[i]) {
			//TODO
			return S.ch[i] - T.ch[i];
		}
	}
	return S.length - T.length;
}

清空串

HString ClearString(HString S) {
	//	将S清为空串
	if (S.ch) {
		//TODO
		free(S.ch);
		S.ch = NULL;
	}
	S.length = 0;
	return S;
}

链接新串

HString Concat(HString T, HString S1, HString S2) {
	//用T返回由S1和S2链接而成的新串
	if (T.ch)
	{
		free(T.ch);//释放旧空间
	}
	if (!(T.ch = (char*)malloc((S1.length + S2.length) * sizeof(char))))
	{
		exit(ERROR);
	}
	for (int i = 0; i < S1.length; i++)
	{
		printf("i=%d\n", i);
		T.ch[i] = S1.ch[i];
	}

	T.length = S1.length + S2.length;
	for (int i = S1.length; i < T.length; i++)
	{
		T.ch[i] = S2.ch[i - S1.length];
	}
	T.ch[T.length] = '\0';
	return T;
}

用Sub返回串S的第pos个字符起长度为len的子串

HString SubString(HString Sub, HString S, int pos, int len) {
	//用Sub返回串S的第pos个字符起长度为len的子串
	//其中，1<=pos<=StrLength(S)&&0<=len<=StrLength(S)-pos+1
	if (pos<1 || pos>S.length || len<0 || len>S.length - pos + 1)
	{
		exit(ERROR);
	}
	if (Sub.ch)
	{
		//释放旧空间
		free(Sub.ch);
	}
	if (!len)
	{
		//空子串
		Sub.ch = NULL;
		Sub.length = 0;
	}
	else
	{
		Sub.ch = (char*)malloc(len * sizeof(char));
		int lengthNum = 0;
		int posNum = 1;
		while (1)
		{
			Sub.ch[lengthNum] = S.ch[posNum];
			lengthNum++;
			posNum++;
			if (posNum == pos + len && posNum <= S.length)
			{
				break;
			}
		}
		Sub.length = len;
		Sub.ch[len] = '\0';
	}
	return Sub;
}