gvsafronov/futriix
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

LCS: implement range indexes option.

Browse Source
This commit is contained in:
antirez 2020-04-01 17:11:31 +02:00
parent 1010c1b43e
commit b3400559be
1 changed files with 59 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
src/t_string.c
View File

@ -482,7 +482,7 @@ void strlenCommand(client *c) {
/* LCS -- Longest common subsequence.
*
* LCS [LEN] [IDX] [STOREIDX <key>] STRINGS <string> <string> */
* LCS [IDX] [STOREIDX <key>] STRINGS <string> <string> */
void lcsCommand(client *c) {
uint32_t i, j;
sds a = NULL, b = NULL;
@ -495,12 +495,12 @@ void lcsCommand(client *c) {
if (!strcasecmp(opt,"IDX")) {
getidx = 1;
} else if (!strcasecmp(opt,"LEN")) {
getlen = 1;
} else if (!strcasecmp(opt,"STOREIDX") && moreargs) {
getidx = 1;
idxkey = c->argv[j+1];
j++;
} else if (!strcasecmp(opt,"LEN")) {
getlen++;
} else if (!strcasecmp(opt,"STRINGS")) {
if (moreargs != 2) {
addReplyError(c,"LCS requires exactly two strings");
@ -515,10 +515,17 @@ void lcsCommand(client *c) {
}
}
/* Complain if the user didn't pass the STRING option. */
/* Complain if the user passed ambiguous parameters. */
if (a == NULL) {
addReplyError(c,"STRINGS <string-a> <string-b> is mandatory");
return;
} else if (getlen && (getidx && idxkey == NULL)) {
addReplyError(c,
"If you want both the LEN and indexes, please "
"store the indexes into a key with STOREIDX. However note "
"that the IDX output also includes both the LCS string and "
"its length");
return;
}
/* Compute the LCS using the vanilla dynamic programming technique of
@ -559,21 +566,62 @@ void lcsCommand(client *c) {
/* Store the actual LCS string in "result" if needed. We create
* it backward, but the length is already known, we store it into idx. */
uint32_t idx = LCS(alen,blen);
sds result = NULL;
sds result = NULL; /* Resulting LCS string. */
void *arraylenptr = NULL; /* Deffered length of the array for IDX. */
uint32_t arange_start = alen, /* alen signals that values are not set. */
arange_end = 0,
brange_start = 0,
brange_end = 0;
/* Do we need to compute the actual LCS string? Allocate it in that case. */
int computelcs = getidx || !getlen;
if (computelcs) result = sdsnewlen(SDS_NOINIT,idx);
/* Start with a deferred array if we have to emit the ranges. */
uint32_t arraylen = 0; /* Number of ranges emitted in the array. */
if (getidx && idxkey == NULL)
arraylenptr = addReplyDeferredLen(c);
i = alen, j = blen;
while (computelcs && i > 0 && j > 0) {
if (a[i-1] == b[j-1]) {
/* If there is a match, store the character and reduce
* the indexes to look for a new match. */
result[idx-1] = a[i-1];
idx--;
i--;
j--;
/* Track the current range. */
int emit_range = 0;
if (arange_start == alen) {
arange_start = i-1;
arange_end = i-1;
brange_start = j-1;
brange_end = j-1;
if (i == 0 || j == 0) emit_range = 1;
} else {
/* Let's see if we can extend the range backward since
* it is contiguous. */
if (arange_start == i && brange_start == j) {
arange_start--;
brange_start--;
} else {
emit_range = 1;
}
}
/* Emit the current range if needed. */
if (emit_range) {
if (arraylenptr) {
addReplyArrayLen(c,2);
addReplyArrayLen(c,2);
addReplyLongLong(c,arange_start);
addReplyLongLong(c,arange_end);
addReplyArrayLen(c,2);
addReplyLongLong(c,brange_start);
addReplyLongLong(c,brange_end);
}
arange_start = alen; /* Restart at the next match. */
arraylen++;
}
idx--; i--; j--;
} else {
/* Otherwise reduce i and j depending on the largest
* LCS between, to understand what direction we need to go. */
@ -589,7 +637,9 @@ void lcsCommand(client *c) {
/* Signal modified key, increment dirty, ... */
/* Reply depending on the given options. */
if (getlen) {
if (arraylenptr) {
setDeferredArrayLen(c,arraylenptr,arraylen);
} else if (getlen) {
addReplyLongLong(c,LCS(alen,blen));
} else {
addReplyBulkSds(c,result);