《数据结构复习》串的堆分配

//串的堆分配实现
//ch1_3
#include<stdio.h>
#include<stdlib.h>
#define OVERFLOW -1
#define OK 1
#define ERROR 0
typedef  int status;

typedef struct {
	char* ch;
	int length;
}HString;
//初始化串
int initstring(HString* S)
{
	S->length = 0;
	S->ch = '\0';
	return OK;
}
//为串分配空间、赋值
int strassign(HString* T, char* chars) {
	if (T->ch)//T不空，释放空间
		free(T->ch);
	char* c = chars;
	int i = 0;					//求串的长度
	for (i = 0; *c; ++i, ++c);//这里面c一定要加*，否则不对
	if (!i) {
		T->ch = NULL; T->length = 0;//i为0，说明为空串
	}
	else {
		T->ch = (char*)malloc(i * sizeof(char));//分配空间
		if (!T->ch)
			exit(OVERFLOW);
		for (int j = 0; j < i; j++)//复制串
			T->ch[j] = chars[j];
		T->length = i;
	}
	return OK;
}
//返回串的长度
int strlength(HString t) {
	return t.length;
}
//比较两串
int strcompare(HString s, HString t) {
	for (int i = 0; i < s.length && i < t.length; i++) {
		if (s.ch[i] != t.ch[i])
			return (s.ch[i] - t.ch[i]);
	}
	return (s.length - t.length);
}
//清空串
status strclearstring(HString* t) {
	if (t->ch) {
		free(t->ch);
		t->ch = NULL;
	}
	t->length = 0;
	return OK;
}
//返回两串连接
status concat(HString* t, HString a, HString b) {
	if (!t->ch)
		free(t->ch);
	if (!(t->ch = (char*)malloc((a.length + b.length) * sizeof(char))))
		exit(OVERFLOW);
	for (int i = 0; i <= a.length - 1; i++) {//先复制a串  <=length-1
		t->ch[i] = a.ch[i];
	}
	for (int i = 0; i <= b.length - 1; i++) {//复制b串    <=length-1
		t->ch[a.length + i] = b.ch[i];
	}
	t->length = a.length + b.length;
	return OK;
}
//返回子串
status substring(HString * a,HString *s, int pos, int len) {
	if (pos<0 || pos>s->length || len<0 || len>s->length - pos + 1)
		return ERROR;
	if (!a->ch)
		free(a->ch);
	if (!len) {//空子串
		a->ch = NULL, a->length = 0;
	}
	else {
		a->ch = (char*)malloc(len * sizeof(char));
		for (int i = 0; i <= len - 1; i++) {
			a->ch[i] = s->ch[i + pos-1];
		}
		a->length = len;
	}
	return OK;
}
//打印串
void strprint(HString a) {
	for (int i = 0; i <= a.length - 1; i++) {
		printf("%c", a.ch[i]);
	}
	printf("\n");
}
int main() {
	HString a, b, c, d;
	initstring(&a);
	strassign(&a, "hello cumtber cyl");
	initstring(&b);
	strassign(&b, "cyl");
	//初始化串
	concat(&c, a, b);	//连接两串
	substring(&d, &a, 3, 3);	//取出子串

	strprint(a);
	strprint(b);
	strprint(c);
	int i=strcompare(a, b);
	strprint(d);
	printf("串的长度：%d\n", a.length);
	printf("%d", i);
	return 0;
}