思想和代码都不难，和线性表也差不多，串本来就是数据受限的线性表。

串连接：

 

#include <stdio.h>
#include <string.h>
//串的定长顺序存储表示
#define MAXSTRLEN 255							//用户可在255以内定义最大串长
typedef unsigned char SString[MAXSTRLEN + 1];	//0号单元存放串的长度int Concat(SString *T,SString S1,SString S2)//用T返回S1和S2联接而成的新串。若未截断返回1，若截断返回0
{int i = 1,j,uncut = 0;if(S1[0] + S2[0] <= MAXSTRLEN)	//未截断{for (i = 1; i <= S1[0]; i++)//赋值时等号不可丢(*T)[i] = S1[i];for (j = 1; j <= S2[0]; j++)(*T)[S1[0]+j] = S2[j];	//(*T)[i+j] = S2[j](*T)[0] = S1[0] + S2[0];uncut = 1;}else if(S1[0] < MAXSTRLEN)		//截断{for (i = 1; i <= S1[0]; i++)//赋值时等号不可丢(*T)[i] = S1[i];for (j = S1[0] + 1; j <= MAXSTRLEN; j++){(*T)[j] = S2[j - S1[0] ];(*T)[0] = MAXSTRLEN;uncut = 0;}}else{for (i = 0; i <= MAXSTRLEN; i++)(*T)[i] = S1[i];/*或者分开赋值，先赋值内容，再赋值长度for (i = 1; i <= MAXSTRLEN; i++)(*T)[i] = S1[i];(*T)[0] = MAXSTRLEN;*/uncut = 0;}return uncut;
}int SubString(SString *Sub,SString 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)且0 ≤ len ≤ StrLength(S) - pos + 1(从pos开始到最后有多少字符)//第1个字符的下标为1,因为第0个字符存放字符长度
{int i;if(pos < 1 || pos > S[0] || len < 0 || len > S[0] - pos + 1)return 0;for (i = 1; i <= len; i++){//S中的[pos,len]的元素 -> *Sub中的[1,len](*Sub)[i] = S[pos + i - 1];//下标运算符 > 寻址运算符的优先级}(*Sub)[0] = len;return 1;
}
void PrintStr(SString S)
{int i;for (i = 1; i <= S[0]; i++)printf("%c",S[i]);printf("\n");
}int main(void)
{/*定长顺序存储初始化和打印的方法SString s = {4,'a','b','c','d'};int i;//s = "abc";	//不可直接赋值for (i = 1; i <= s[0]; i++)printf("%c",s[i]);*/SString s1 = {4,'a','b','c','d'};SString s2 = {4,'e','f','g','h'},s3;SString T,Sub;int i;for (i = 1; i <= 255; i++){s3[i] = 'a';if(i >= 248)s3[i] = 'K';}s3[0] = 255;SubString(&Sub,s3,247,8);PrintStr(Sub);return 0;
}