#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0
#define OVERFLOW -2
#define STR_INIT_SIZE 100
#define STRINCREMENT 10
typedef int Status;
typedef struct
{
  char *ch; //空串時指向NULL,非空串時按串長分配存儲區(qū)
  int length;
} HString;
Status InitString(HString *T) //初始化字符串
{
  //指針指向NULL,長度為0即可
  //p.s.申請內(nèi)存空間的過程在賦值中完成
  T->ch = NULL;
  T->length = 0;
  return OK;
}
Status StrAssign(HString *T, char *p) //字符串賦值
{
  //1.判斷T是否已有內(nèi)容,有則釋放
  //2.判斷賦值的內(nèi)容是否為空,為空則不賦值
  //3.根據(jù)長度向內(nèi)存申請空間,遍歷賦值給T,長度等于字符串長度
  //p.s.在這里賦值不賦\0,在打印時通過長度來判斷字符串結(jié)尾
  int i, len = strlen(p);
  if (T->ch)
    free(T->ch);
  if (!len)
  {
    T->ch = NULL;
    T->length = 0;
    return ERROR;
  }
  else
  {
    T->ch = (char *)malloc(len * sizeof(char));
    if(!T->ch)
      exit(OVERFLOW);
    for (i = 0; i < len; ++i)
      T->ch[i] = p[i];
    T->length = len;
    return OK;
  }
}
Status StrPrint(HString T) //打印字符串
{
  //通過長度判斷打印的字符數(shù)
  int i;
  for (i = 0; i < T.length; ++i)
    printf("%c", T.ch[i]);
  printf("\n");
}
Status StrLength(HString T) //字符串長度
{
  return T.length;
}
Status StrEmpty(HString T) //字符串判空
{
  if (T.length == 0)
    return TRUE;
  else
    return FALSE;
}
Status Concat(HString *T, HString S1, HString S2) //字符串聯(lián)接
{
  //1.申請長度為S1和S2之和的字符串空間
  //2.先將S1的元素逐個賦值到T中
  //3.再將S2的元素逐個賦值到T中
  int i;
  if (T->ch)
    free(T->ch);
  T->ch = (char *)malloc((S1.length + S2.length) * sizeof(char));
  if (!T->ch)
    exit(OVERFLOW);
  for (i = 0; i < S1.length; ++i)
    T->ch[i] = S1.ch[i];
  for (i = 0; i < S2.length; ++i)
    T->ch[i + S1.length] = S2.ch[i];
  T->length = S1.length + S2.length;
  return OK;
}
Status StrDelete(HString *T, int pos, int len) //刪除字符串中某個位置固定長度的子串
{
  //pos是字符串中的位置,刪除包括pos的len長度
  int i;
  if (pos >= T->length)
    return ERROR;
  else if(pos + len > T->length)
    len = T->length - pos + 1;
  for (i = pos - 1; i < T->length - len; ++i)
    T->ch[i] = T->ch[i + len];
  T->length -= len;
  T->ch = (char *)realloc(T->ch, T->length * sizeof(char));
  if (!T->ch)
    exit(OVERFLOW);
  return OK;
}
Status StrInsert(HString *S, int pos, HString T)
{
  //pos是字符串中的位置,插入時原來的元素(包括pos位)后移
  int i, len;
  --pos;
  len = StrLength(T);
  S->ch = (char *)realloc(S->ch, (S->length + len) * sizeof(char));
  if (pos > S->length)
    pos = S->length;
  for (i = S->length - 1; i > pos - 1; --i)
    S->ch[i + len] = S->ch[i];
  for (i = 0; i < len; ++i)
    S->ch[i + pos] = T.ch[i];
  S->length += len;
  if (!S->ch)
    exit(OVERFLOW);
  return OK;
}
Status Index(HString S, HString T, int pos) //在字符串S中索引位置pos之后的子串t
{
  //同定長順序存儲表示法
  //p.s.傳入的pos是字符串的位置,從1開始
  //p.s.初始狀態(tài)下T為非空串
  if (StrEmpty(T))
    return ERROR;
  int i = pos - 1, j = 0;
  while(i < S.length && j < T.length)
  {
    if (S.ch[i] == T.ch[j])
    {
      ++i;
      ++j;
    }
    else
    {
      i = i - j + 1;
      j = 0;
    }
  }
  if (j >= T.length)
    return i - j + 1;
  else
    return 0;
}
Status Replace(HString *T, HString S1, HString S2) //將字符串T中等于S1的子串替換成為S2
{
  //循環(huán)索引子串S1在字符串T中的位置(每次的位置從上一次位置后開始查找)
  //從查找到的位置-1開始替換
  //p.s.初始狀態(tài)下S1為非空串
  int pos = 0;
  if (StrEmpty(S1))
    return ERROR;
  //當pos存在時循環(huán),當全部索引完畢后pos為0
  //將索引到的該位置對應的子串刪除后再插入新的子串
  do
  {
    pos = Index(*T, S1, pos);
    if (pos)
    {
      StrDelete(T, pos, StrLength(S1));
      StrInsert(T, pos, S2);
    }
  }
  while(pos);
  return OK;
}
Status SubString(HString *Sub, HString S, int pos, int len)
{
  int i;
  if (pos < 1 || len > S.length || len < 0 || len > S.length - pos + 1)
    exit(OVERFLOW);
  if (Sub->ch)
    free(Sub->ch);
  //如果查詢的長度為0,則子串置空
  if (len == 0)
  {
    Sub->ch = NULL;
    Sub->length = 0;
  }
  else
  {
    Sub->ch = (char *)malloc(len * sizeof(char));
    for (i = 0; i < len; ++i)
      Sub->ch[i] = S.ch[pos + i - 1];
    Sub->length = len;
  }
  return OK;
}
int main()
{
  int pos;
  HString t, s, r;
  char *p = "Hello,String!", *q = "Bye,Bye!";
  printf("String *p: %s\n", p);
  InitString(&t);
  StrAssign(&t, p);
  printf("StrAssign... OK.\nString t : ");
  StrPrint(t);
  printf("------------------------------\n");
  printf("StrLength... OK.\nString Length : %d\n", StrLength(t));
  printf("StrEmpty... OK.\n");
  if (StrEmpty(t))
    printf("String is Empty.\n");
  else
    printf("String is not Empty.\n");
  printf("------------------------------\n");
  InitString(&s);
  StrAssign(&s, q);
  printf("String s : ");
  StrPrint(s);
  printf("------------------------------\n");
  InitString(&r);
  Concat(&r, t, s);
  printf("Concat... OK.\n");
  printf("String r : ");
  StrPrint(r);
  printf("------------------------------\n");
  printf("StrDelete... OK.\n");
  StrDelete(&r, 14, 4);
  printf("String r : ");
  StrPrint(r);
  printf("------------------------------\n");
  printf("StrInsert... OK.\n");
  StrAssign(&t, "Bye,Bye,Bye!");
  StrInsert(&r, 14, t);
  printf("String r : ");
  StrPrint(r);
  printf("------------------------------\n");
  StrAssign(&t, "ye");
  printf("Index... ");
  StrPrint(t);
  pos = 1;
  while(pos)
  {
    pos = Index(r, t, pos + 1);
    if (!pos)
      break;
    printf("Position : %d\n", pos);
  }
  printf("------------------------------\n");
  StrAssign(&t, "ye");
  StrAssign(&s, "oo");
  Replace(&r, t, s);
  printf("Replace ye -> ooo ... OK.\n");
  printf("String r : ");
  StrPrint(r);
  printf("------------------------------\n");
  SubString(&t, r, 7, 4);
  printf("SubString... OK.\n");
  printf("String SubString : ");
  StrPrint(t);
  printf("------------------------------\n");
  return OK;
}