串是字符串的簡稱。它是一種在數(shù)據(jù)元素的組成上具有一定約束條件的線性表，即要求組成線性表的所有數(shù)據(jù)元素都是字符，所以，人們經(jīng)常這樣定義串：串是一個有窮字符序列。如： abcdef

串的長度為6

串中沒有任何字符，其串的長度為0，通常稱為空串。由空格字符組成的串，一班稱為空格串。串中任意連續(xù)的字符組成的子序列稱為該串的子串。包含子串的串又稱為該子串的主串。子串在主串中第一次出現(xiàn)的第一個字符的位置稱為子串在主串中的位置。兩個串的長度相等，并且各個對應的字符都相同，稱兩個串相等。串的存儲方式也分兩種：串的順序存儲結構和串的鏈式存儲結構

我寫的是一個堆分配存儲的串，代碼：

#include<iostream>#include<string>#include<malloc.h>using namespace std;//串的堆存儲方式typedef struct {	char *str;	int length;}HString;void init(HString  *s) {	s->length = 0;	s->str = NULL;}//串初始化void HStringInit(HString *s) {	char c;	int length;	cout << "請輸入串的長度：" << endl;	cin >> length;	s->length = length;	s->str = (char*)malloc((length+1)*sizeof(char));	for (int i = 0; i < s->length; i++) {		cin >> c;		s->str[i] = c;	}	cout << "初始化成功！" << endl;}//串賦值void HStringAssign(HString *s, HString *t) {				if (s->str) free(s->str);	int len = t->length;	s->length = len;	if (!len) {		s->str = (char*)malloc(sizeof(char));		s->str[0] = '/0';	}	else {		s->str = (char*)malloc(sizeof(char));		for (int i = 0; i < t->length; i++) {			s->str[i] = t->str[i];		}	}	cout << "賦值成功！" << endl;}//輸出串內(nèi)容void PRint(HString *s) {								if (s->length == 0 && s->str == NULL) {		cout << "串的內(nèi)容為空！" << endl;	}	else {		cout << "串的內(nèi)容為：	";		for (int i = 0; i < s->length; i++) {			cout << s->str[i];		}		cout << endl;	}}//求串長void HStringLength(HString *s ) {						cout << "串的長度為：		" << s->length << endl;}//判串相等void HStringCompar(HString *s,HString *t) {					int flag = 0;	if (s->length != t->length) {		cout << "不相等！" << endl;	}	else {		if (s->length == 0) {			cout << "相等！" << endl;		}		else {			for (int i = 0; i < s->length&&i < t->length; i++) {				if (s->str[i] != t->str[i]) {					cout << "不相等！" << endl;					flag = 1;					break;				}			}			if (flag == 0) {				cout << "相等！" << endl;			}		}	}}//串連接void HStringConCat(HString *s,HString *t) {					HString s1;	init(&s1);	int i = 0;	HStringAssign(&s1, s);	s->length += t->length;	free(s->str);	s->str = (char*)malloc((s->length+1)*sizeof(char));	for (; i < s1.length; i++) {		s->str[i] = s1.str[i];	}	for (; i < s->length;i++) {		s->str[i] = t->str[i - s1.length];	}	free(s1.str);	free(t->str);	t->str = NULL;	t->length = 0;	cout << "連接完成！" << endl;}//求子串void HStringSub(HString *s,int start,int end) {				cout << "子串為：";	for (int i = start - 1; i < end; i++) {		cout << s->str[i];	}	cout << endl;}//子串定位void HStringIndex(HString *s,HString *t) {					int i = 0,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) {		cout << "子串的位置為:" << i-t->length + 1 << endl;	}	else {		cout << "沒有該子串！" << endl;	}}//串置換void HStringReplace(HString *s,HString *t) {			HString s1;	init(&s1);	HStringAssign(&s1, s);	HStringAssign(s, t);	HStringAssign(t, &s1);	free(s1.str);	s1.length = 0;	s1.str = NULL;	cout << "置換成功！" << endl;}//插入子串void HStringInsert(HString *s,int start,HString *t) {		HString s1;	init(&s1);	int i = 0,j;	HStringAssign(&s1, s);	s->length += t->length;	free(s->str);	s->str = (char*)malloc((s->length + 1) * sizeof(char));	for (; i < start-1; i++) {		s->str[i] = s1.str[i];	}	j = i;	for (int k = 0; k < t->length; k++, i++) {		s->str[i] = t->str[k];	}	for (; i < s->length; i++, j++) {		s->str[i] = s1.str[j];	}	cout << "插入成功！" << endl;}//刪除子串void HStringDelet(HString *s,int start,int length) {		int i = start,flag,k=length;	char c;	while (length != 0) {		s->str[i - 1] = 0;		length--;		i++;	}	for (int m = 0; m < s->length;m++) {		if (s->str[m] != 0 && s->str[m - 1] == 0) {			flag = m;			while (flag) {				if (s->str[flag - 1] != 0) {					break;				}				c = s->str[flag - 1];				s->str[flag - 1] = s->str[flag];				s->str[flag] = c;				flag--;			}		}	}	s->length -=k;	cout << "刪除成功！" << endl;}void message() {	cout << "************************************************************" << endl;	cout << "*	1  	輸出串          	2	串賦值	   *" << endl;	cout << "*	3	判串相等		4	求串長	   *" << endl;	cout << "*	5	串連接			6	求子串	   *" << endl;	cout << "*	7	子串定位		8	串置換	   *" << endl;	cout << "*	9	插入子串		10	刪除子串   *" << endl;	cout << "*	11	清屏			12	退出	   *" << endl;	cout << "************************************************************" << endl;}void main() {	int temp = 0,length;	HString S1, S2;	message();	cout << "對串S1進行初始化：" << endl;	HStringInit(&S1);	cout << "對串S2進行初始化：" << endl;	HStringInit(&S2);	int i = 0;	while (1) {				cin >> i;		switch (i) {		case 1:cout << "請輸入你要輸出的串    1:  S1,    2:   S2" << endl;										cin >> temp;					switch (temp) {							case 1:print(&S1); break;							case 2:print(&S2); break;							default:cout << "輸入錯誤！" << endl; break;					}				break;		case 2:	cout << "將S2賦值給S1" << endl;					HStringAssign(&S1, &S2);				break;		case 3:cout << "判斷S1和S2是否相等？" << endl;					HStringCompar(&S1, &S2);				break;		case 4:cout << "請輸入你要求的串    1:  S1,    2:   S2" << endl;					cin >> temp;					switch (temp) {							case 1:HStringLength(&S1); break;							case 2:HStringLength(&S2); break;							default:cout << "輸入錯誤！" << endl; break;					}				break;		case 5:cout << "將串S2連接到S1上！" << endl;					HStringConCat(&S1, &S2);				break;		case 6:cout << "求S1的子串：" << endl;				cout << "請輸入開始位置和長度：" << endl;				cin >> temp >> length;				if (temp > S1.length) {					cout << "輸出位置錯誤！" << endl;					break;				}				else {					if ((length - temp) > S1.length) {						cout << "子串長度超出！" << endl;					}					else {						HStringSub(&S1, temp, length);					}				}				break;		case 7:cout << "子串S2在S1中的位置" << endl;			HStringIndex(&S1,&S2);			break;		case 8:cout << "將S1和S2置換！" << endl;				HStringReplace(&S1,&S2);			break;		case 9:cout << "將S2插入到S1中" << endl;				cout << "請輸入插入位置：" << endl;				cin >> temp;				if (temp >= S1.length) {					cout << "插入位置錯誤！" << endl;					break;				}				else {					HStringInsert(&S1,temp,&S2);				}			break;		case 10:cout << "刪除S1的子串：" << endl;				cout << "請輸入開始位置和長度：" << endl;				cin >> temp >> length;				if (temp > S1.length) {					cout << "輸出位置錯誤！" << endl;					break;				}				else {					if ((length + temp) > S1.length+1) {					cout << "子串長度超出！" << endl;					}					else {						HStringDelet(&S1, temp, length);					}				}break;		case 11:system("cls"); message(); break;		case 12:exit(0); break;		default:cout << "輸入錯誤！請重新輸入：" << endl; break;		}	}}