#include<stdio.h>
#define MAXSIZE 100
typedef struct {
char str[MAXSIZE];
int length;
}seq;


void strinsert(seq *s, int i, seq t)
{
if (i<1 || i>MAXSIZE + 1 || s->length + t.length > MAXSIZE)
printf("不能進行插入！\n");
else
{
int k;
for (k = s->length - 1; k >= i - 1; k--)
s->str[k + t.length] = s->str[k];
for (k = 0; k < t.length; k++)
s->str[i - 1 + k] = t.str[k];
s->length = s->length + t.length;
s->str[s->length] = '\0';
}
}


void strdele(seq *s, int i, int len)
{
if (i<1 || i>MAXSIZE + 1 || i+len>s->length+1)
printf("不能進行刪除！\n");
else
{
int k;
for (k = i - 1+len; k <s->length; k++)
s->str[k -len] = s->str[k];
s->length = s->length -len;
s->str[s->length] = '\0';
}
}


seq *strconcat(seq s1, seq s2)
{
seq *s;
s = (seq *)malloc(sizeof(seq));
int k;
for (k = 0; k < s1.length; k++)
s->str[k] = s1.str[k];
s->length = s1.length;
if (s1.length + s2.length > MAXSIZE)
{
for (k = 0; k + s->length + 1 < MAXSIZE; k++)
s->str[s->length + k] = s2.str[k];
s->length = MAXSIZE;
s->str[s->length] = '\0';
}
else
{
for (k = 0; k < s2.length; k++)
s->str[s->length + k] = s2.str[k];
s->length = s1.length+s2.length;
s->str[s->length] = '\0';
}
return s;
}


seq *substring(seq s, int i, int len)
{
seq *t;
t = (seq *)malloc(sizeof(seq));
if (i<1 || i>MAXSIZE + 1 ||i+len-1 > MAXSIZE)
printf("沒有這樣的字串！\n");
else
{
int k;
for (k = 0; k < len; k++)
t->str[k] = s.str[k+i-1];
t->length =len;
t->str[t->length] = '\0';
}
return t;
}


void display(seq S)
{
int i;
for (i = 0; i < S.length; i++)
printf("%5c", S.str[i]);
putchar('\n');
}


void main()
{
seq *s;
s = (seq *)malloc(sizeof(seq));
seq *t;
t = (seq *)malloc(sizeof(seq));
s->str[0] = 'A';
s->str[1] = 'B';
t->str[0] = 'C';
t->str[1] = 'D';
s->length = 2;
t->length = 2;
display(*s);
display(*t);
strinsert(s, 3, *t);
display(*s);
strinsert(s, 3, *s);
display(*s);
strdele(s, 3, 3);
display(*s);
s = strconcat(*s, *t);
display(*s);
t = substring(*s, 2, 3);
display(*t);
}