C语言去除相邻重复字符函数的实现方法分享

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C语言去除相邻重复字符函数的实现方法

字符去重函数

功能：去重字符串相邻重复的字符，不相邻的不用去重

参数：

arg1 — 输入字符串
arg2 — 字符串开始位置
arg3 — 字符串结束位置

要求：

输入参数为arg1时， 对这个字符串去重
输入参数为arg1，arg2时， 从arg2位置到字符串结束，去重
输入参数为arg1，arg2，arg3时，从arg2到arg3位置，去重

src/include/catalog/pg_proc.h

  DATA(insert OID = 6669 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 25 "25" _null_ _null_ _null_ _null_ _null_ remove_dup_char_arg1 _null_ _null_ _null_ ));  DESCR("Remove duplicate characters.");  DATA(insert OID = 6670 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 25 "25 23" _null_ _null_ _null_ _null_ _null_ remove_dup_char_arg2 _null_ _null_ _null_ ));  DESCR("Remove duplicate characters.");  DATA(insert OID = 6671 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 3 0 25 "25 23 23" _null_ _null_ _null_ _null_ _null_ remove_dup_char_arg3 _null_ _null_ _null_ ));  DESCR("Remove duplicate characters.");

 src/backend/utils/adt/myfuncs.c

  /*    * Remove duplicate characters    * author:young   */  Datum   remove_dup_char_arg1 (PG_FUNCTION_ARGS)  {   int n = 0;   text *arg0 = PG_GETARG_TEXT_P(0);     char *str = text_to_cstring(arg0);   n = strlen(str);     remove_dup(str, 0, n);     PG_RETURN_TEXT_P(cstring_to_text(str));  }    Datum   remove_dup_char_arg2 (PG_FUNCTION_ARGS)  {   int n = 0;   text *arg0 = PG_GETARG_TEXT_P(0);   int32 arg1 = PG_GETARG_INT32(1);     char *str = text_to_cstring(arg0);   n = strlen(str);     if (!(1 <= arg1 && arg1 <= n))   {   ereport(ERROR,    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),    errmsg("out of range")));   }     remove_dup(str, arg1 - 1, n);     PG_RETURN_TEXT_P(cstring_to_text(str));  }    Datum   remove_dup_char_arg3 (PG_FUNCTION_ARGS)  {   int n = 0;   text *arg0 = PG_GETARG_TEXT_P(0);   int32 arg1 = PG_GETARG_INT32(1);   int32 arg2 = PG_GETARG_INT32(2);     char *str = text_to_cstring(arg0);   n = strlen(str);     if (!(1 <= arg1 && arg1 <= arg2 && arg2 <= n))   {   ereport(ERROR,    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),    errmsg("out of range")));   }     remove_dup(str, arg1 - 1, arg2 - 1);     PG_RETURN_TEXT_P(cstring_to_text(str));  }    void   remove_dup(char *str, int start, int end)  {   int i = start, k = start;     for (i = start; i <= end; i++)    {   if (str[i + 1] && str[i + 1] == str[i] && i + 1 <= end)   {    k++;   }    else    {    str[i-k] = str[i];   }      }   str[i-k] = '';  }    

比较繁琐，再做一下修改，三个函数放到一个中

src/include/catalog/pg_proc.h

  DATA(insert OID = 6669 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 25 "25" _null_ _null_ _null_ _null_ _null_ remove_dup_char _null_ _null_ _null_ ));  DESCR("Remove duplicate characters.");  DATA(insert OID = 6670 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 25 "25 23" _null_ _null_ _null_ _null_ _null_ remove_dup_char _null_ _null_ _null_ ));  DESCR("Remove duplicate characters.");  DATA(insert OID = 6671 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 3 0 25 "25 23 23" _null_ _null_ _null_ _null_ _null_ remove_dup_char _null_ _null_ _null_ ));  DESCR("Remove duplicate characters.");  

src/backend/utils/adt/myfuncs.c

添加定义：

  #define PG_GETARG_IF_EXISTS(n, type, defval)    ((PG_NARGS() > (n) && !PG_ARGISNULL(n)) ? PG_GETARG_##type(n) : (defval)) 

 修改方法：

  /*    * Remove duplicate characters    * author:yangjie   */  Datum   remove_dup_char (PG_FUNCTION_ARGS)  {   text *arg0 = PG_GETARG_IF_EXISTS(0, TEXT_P, NULL);   int32 arg1 = PG_GETARG_IF_EXISTS(1, INT32, 0);   int32 arg2 = PG_GETARG_IF_EXISTS(2, INT32, 0);   int n = 0;     char *str = text_to_cstring(arg0);   n = strlen(str);     if(PG_NARGS() == 1)   {   remove_dup(str, 0, n);   }     if(PG_NARGS() == 2)   {   if (!(1 <= arg1 && arg1 <= n))   {    ereport(ERROR,    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),    errmsg("out of range")));   }   remove_dup(str, arg1 - 1, n);   }     if(PG_NARGS() == 3)   {   if (!(1 <= arg1 && arg1 <= arg2 && arg2 <= n))   {    ereport(ERROR,    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),    errmsg("out of range")));   }   remove_dup(str, arg1 - 1, arg2 - 1);   }     PG_RETURN_TEXT_P(cstring_to_text(str));  }    

 再修改一下，如果有输入参数就用 没有就用默认值  最后再去重处理减少代码重用

  /*    * Remove duplicate characters    * author:yangjie   */  Datum   remove_dup_char (PG_FUNCTION_ARGS)  {   text *arg0 = PG_GETARG_IF_EXISTS(0, TEXT_P, NULL);   int n = 0;   char *str = text_to_cstring(arg0);   n = strlen(str);   int32 arg1 = PG_GETARG_IF_EXISTS(1, INT32, 0);   int32 arg2 = PG_GETARG_IF_EXISTS(2, INT32, n);      if (!(1 <= arg1 && arg1 <= n))   {   ereport(ERROR,    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),    errmsg("1 <= arg1 && arg1 <= n")));   }     if (!(1 <= arg1 && arg1 <= arg2 && arg2 <= n))   {   ereport(ERROR,    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),    errmsg("1 <= arg1 && arg1 <= arg2 && arg2 <= n")));   }     remove_dup(str, arg1, arg2);      PG_RETURN_TEXT_P(cstring_to_text(str));  }    void   remove_dup(char *str, int start, int end)  {   int i = start -1, k = start - 1;     for (i = start - 1; i <= end - 1; i++)    {   if (str[i + 1] && str[i + 1] == str[i] && i + 1 <= end - 1)   {    k++;   }    else    {    str[i-k] = str[i];   }      }   str[i-k] = '';  }       

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