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Java/DynamicProgramming/RegexMatching.java at master · AmaranthLIS/Java · GitHub
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package
DynamicProgramming
;
/**
* Given a text and wildcard pattern implement a wildcard pattern matching
* algorithm that finds if wildcard is matched with text. The matching should
* cover the entire text
* ?-> matches single characters
* *-> match the sequence of characters
**/
/**
* For calculation of Time and Space Complexity. Let N be length of src and M be length of pat
**/
public
class
RegexMatching
{
// Method 1: Using Recursion
// Time Complexity=0(2^(N+M)) Space Complexity=Recursion Extra Space
static
boolean
regexRecursion
(
String
src
,
String
pat
) {
if
(
src
.
length
() ==
0
&&
pat
.
length
() ==
0
) {
return
true
;
}
if
(
src
.
length
() !=
0
&&
pat
.
length
() ==
0
) {
return
false
;
}
if
(
src
.
length
() ==
0
&&
pat
.
length
() !=
0
) {
for
(
int
i
=
0
;
i
<
pat
.
length
();
i
++) {
if
(
pat
.
charAt
(
i
) !=
'*'
) {
return
false
;
}
}
return
true
;
}
char
chs
=
src
.
charAt
(
0
);
char
chp
=
pat
.
charAt
(
0
);
String
ros
=
src
.
substring
(
1
);
String
rop
=
pat
.
substring
(
1
);
boolean
ans
;
if
(
chs
==
chp
||
chp
==
'?'
) {
ans
=
regexRecursion
(
ros
,
rop
);
}
else
if
(
chp
==
'*'
) {
boolean
blank
=
regexRecursion
(
src
,
rop
);
boolean
multiple
=
regexRecursion
(
ros
,
pat
);
ans
=
blank
||
multiple
;
}
else
{
ans
=
false
;
}
return
ans
;
}
// Method 2: Using Recursion and breaking string using virtual index
// Time Complexity=0(2^(N+M)) Space Complexity=Recursion Extra Space
static
boolean
regexRecursion
(
String
src
,
String
pat
,
int
svidx
,
int
pvidx
) {
if
(
src
.
length
() ==
svidx
&&
pat
.
length
() ==
pvidx
) {
return
true
;
}
if
(
src
.
length
() !=
svidx
&&
pat
.
length
() ==
pvidx
) {
return
false
;
}
if
(
src
.
length
() ==
svidx
&&
pat
.
length
() !=
pvidx
) {
for
(
int
i
=
pvidx
;
i
<
pat
.
length
();
i
++) {
if
(
pat
.
charAt
(
i
) !=
'*'
) {
return
false
;
}
}
return
true
;
}
char
chs
=
src
.
charAt
(
svidx
);
char
chp
=
pat
.
charAt
(
pvidx
);
boolean
ans
;
if
(
chs
==
chp
||
chp
==
'?'
) {
ans
=
regexRecursion
(
src
,
pat
,
svidx
+
1
,
pvidx
+
1
);
}
else
if
(
chp
==
'*'
) {
boolean
blank
=
regexRecursion
(
src
,
pat
,
svidx
,
pvidx
+
1
);
boolean
multiple
=
regexRecursion
(
src
,
pat
,
svidx
+
1
,
pvidx
);
ans
=
blank
||
multiple
;
}
else
{
ans
=
false
;
}
return
ans
;
}
// Method 3: Top-Down DP(Memoization)
// Time Complexity=0(N*M) Space Complexity=0(N*M)+Recursion Extra Space
static
boolean
regexRecursion
(
String
src
,
String
pat
,
int
svidx
,
int
pvidx
,
int
[][]
strg
) {
if
(
src
.
length
() ==
svidx
&&
pat
.
length
() ==
pvidx
) {
return
true
;
}
if
(
src
.
length
() !=
svidx
&&
pat
.
length
() ==
pvidx
) {
return
false
;
}
if
(
src
.
length
() ==
svidx
&&
pat
.
length
() !=
pvidx
) {
for
(
int
i
=
pvidx
;
i
<
pat
.
length
();
i
++) {
if
(
pat
.
charAt
(
i
) !=
'*'
) {
return
false
;
}
}
return
true
;
}
if
(
strg
[
svidx
][
pvidx
] !=
0
) {
return
strg
[
svidx
][
pvidx
] ==
1
?
false
:
true
;
}
char
chs
=
src
.
charAt
(
svidx
);
char
chp
=
pat
.
charAt
(
pvidx
);
boolean
ans
;
if
(
chs
==
chp
||
chp
==
'?'
) {
ans
=
regexRecursion
(
src
,
pat
,
svidx
+
1
,
pvidx
+
1
,
strg
);
}
else
if
(
chp
==
'*'
) {
boolean
blank
=
regexRecursion
(
src
,
pat
,
svidx
,
pvidx
+
1
,
strg
);
boolean
multiple
=
regexRecursion
(
src
,
pat
,
svidx
+
1
,
pvidx
,
strg
);
ans
=
blank
||
multiple
;
}
else
{
ans
=
false
;
}
strg
[
svidx
][
pvidx
] =
ans
==
false
?
1
:
2
;
return
ans
;
}
// Method 4: Bottom-Up DP(Tabulation)
// Time Complexity=0(N*M) Space Complexity=0(N*M)
static
boolean
regexBU
(
String
src
,
String
pat
) {
boolean
strg
[][] =
new
boolean
[
src
.
length
() +
1
][
pat
.
length
() +
1
];
strg
[
src
.
length
()][
pat
.
length
()] =
true
;
for
(
int
row
=
src
.
length
();
row
>=
0
;
row
--) {
for
(
int
col
=
pat
.
length
() -
1
;
col
>=
0
;
col
--) {
if
(
row
==
src
.
length
()) {
if
(
pat
.
charAt
(
col
) ==
'*'
) {
strg
[
row
][
col
] =
strg
[
row
][
col
+
1
];
}
else
{
strg
[
row
][
col
] =
false
;
}
}
else
{
char
chs
=
src
.
charAt
(
row
);
char
chp
=
pat
.
charAt
(
col
);
boolean
ans
;
if
(
chs
==
chp
||
chp
==
'?'
) {
ans
=
strg
[
row
+
1
][
col
+
1
];
}
else
if
(
chp
==
'*'
) {
boolean
blank
=
strg
[
row
][
col
+
1
];
boolean
multiple
=
strg
[
row
+
1
][
col
];
ans
=
blank
||
multiple
;
}
else
{
ans
=
false
;
}
strg
[
row
][
col
] =
ans
;
}
}
}
return
strg
[
0
][
0
];
}
public
static
void
main
(
String
[]
args
) {
String
src
=
"aa"
;
String
pat
=
"*"
;
System
.
out
.
println
(
"Method 1: "
+
regexRecursion
(
src
,
pat
));
System
.
out
.
println
(
"Method 2: "
+
regexRecursion
(
src
,
pat
,
0
,
0
));
System
.
out
.
println
(
"Method 3: "
+
regexRecursion
(
src
,
pat
,
0
,
0
,
new
int
[
src
.
length
()][
pat
.
length
()]));
System
.
out
.
println
(
"Method 4: "
+
regexBU
(
src
,
pat
));
}
}
// Memoization vs Tabulation : https://www.geeksforgeeks.org/tabulation-vs-memoization/
// Question Link : https://practice.geeksforgeeks.org/problems/wildcard-pattern-matching/1
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