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C語言去除相鄰重復字符函數的實現方法
字符去重函數
功能：去重字符串相鄰重復的字符，不相鄰的不用去重
參數：
arg1 -- 輸入字符串
arg2 -- 字符串開始位置
arg3 -- 字符串結束位置
要求：
輸入參數為arg1時， 對這個字符串去重
輸入參數為arg1，arg2時， 從arg2位置到字符串結束，去重
輸入參數為arg1，arg2，arg3時，從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] = '\0';
}
比較繁瑣，再做一下修改，三個函數放到一個中
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
添加定義：
#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，如果有輸入參數就用 沒有就用默認值 最后再去重處理減少代碼重用
/*
* 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] = '\0';
}
以上就是C語言去除相鄰重復字符函數的實現方法，如有疑問請留言或者到本站社區交流討論，感謝閱讀，希望能幫助到大家，謝謝大家對本站的支持！
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