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
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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.");
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src/backend/utils/adt/myfuncs.c
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/*
* 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';
}
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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
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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.");
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src/backend/utils/adt/myfuncs.c
添加定义：
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#define PG_GETARG_IF_EXISTS(n, type, defval) \
((PG_NARGS() > (n) && !PG_ARGISNULL(n)) ? PG_GETARG_##type(n) : (defval))
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修改方法：
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/*
* 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));
}
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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
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/*
* 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';
}
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PS：在线文本去重复工具 https://tool.zzvips.com/t/quchong/
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原文链接：https://my.oschina.net/yonj1e/blog/873559