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Java/divideconquer/ClosestPair.java at dev · primary-code-test/Java · GitHub
primary-code-test
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divideconquer
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ClosestPair.java
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package
divideconquer
;
/**
* For a set of points in a coordinates system (10000 maximum), ClosestPair class calculates the two
* closest points.
*
* @author: anonymous
* @author: Marisa Afuera
*/
public
final
class
ClosestPair
{
/** Number of points */
int
numberPoints
=
0
;
/** Input data, maximum 10000. */
private
Location
[]
array
;
/** Minimum point coordinate. */
Location
point1
=
null
;
/** Minimum point coordinate. */
Location
point2
=
null
;
/** Minimum point length. */
private
static
double
minNum
=
Double
.
MAX_VALUE
;
public
static
void
setMinNum
(
double
minNum
) {
ClosestPair
.
minNum
=
minNum
;
}
public
static
void
setSecondCount
(
int
secondCount
) {
ClosestPair
.
secondCount
=
secondCount
;
}
/** secondCount */
private
static
int
secondCount
=
0
;
/** Constructor. */
ClosestPair
(
int
points
) {
numberPoints
=
points
;
array
=
new
Location
[
numberPoints
];
}
/** Location class is an auxiliary type to keep points coordinates. */
public
static
class
Location
{
double
x
=
0
;
double
y
=
0
;
/**
* @param xpar (IN Parameter) x coordinate <br>
* @param ypar (IN Parameter) y coordinate <br>
*/
Location
(
final
double
xpar
,
final
double
ypar
) {
// Save x, y coordinates
this
.
x
=
xpar
;
this
.
y
=
ypar
;
}
}
public
Location
[]
createLocation
(
int
numberValues
) {
return
new
Location
[
numberValues
];
}
public
Location
buildLocation
(
double
x
,
double
y
) {
return
new
Location
(
x
,
y
);
}
/**
* xPartition function: arrange x-axis.
*
* @param a (IN Parameter) array of points <br>
* @param first (IN Parameter) first point <br>
* @param last (IN Parameter) last point <br>
* @return pivot index
*/
public
int
xPartition
(
final
Location
[]
a
,
final
int
first
,
final
int
last
) {
Location
pivot
=
a
[
last
];
// pivot
int
i
=
first
-
1
;
Location
temp
;
// Temporarily store value for position transformation
for
(
int
j
=
first
;
j
<=
last
-
1
;
j
++) {
if
(
a
[
j
].
x
<=
pivot
.
x
) {
// Less than or less than pivot
i
++;
temp
=
a
[
i
];
// array[i] <-> array[j]
a
[
i
] =
a
[
j
];
a
[
j
] =
temp
;
}
}
i
++;
temp
=
a
[
i
];
// array[pivot] <-> array[i]
a
[
i
] =
a
[
last
];
a
[
last
] =
temp
;
return
i
;
// pivot index
}
/**
* yPartition function: arrange y-axis.
*
* @param a (IN Parameter) array of points <br>
* @param first (IN Parameter) first point <br>
* @param last (IN Parameter) last point <br>
* @return pivot index
*/
public
int
yPartition
(
final
Location
[]
a
,
final
int
first
,
final
int
last
) {
Location
pivot
=
a
[
last
];
// pivot
int
i
=
first
-
1
;
Location
temp
;
// Temporarily store value for position transformation
for
(
int
j
=
first
;
j
<=
last
-
1
;
j
++) {
if
(
a
[
j
].
y
<=
pivot
.
y
) {
// Less than or less than pivot
i
++;
temp
=
a
[
i
];
// array[i] <-> array[j]
a
[
i
] =
a
[
j
];
a
[
j
] =
temp
;
}
}
i
++;
temp
=
a
[
i
];
// array[pivot] <-> array[i]
a
[
i
] =
a
[
last
];
a
[
last
] =
temp
;
return
i
;
// pivot index
}
/**
* xQuickSort function: //x-axis Quick Sorting.
*
* @param a (IN Parameter) array of points <br>
* @param first (IN Parameter) first point <br>
* @param last (IN Parameter) last point <br>
*/
public
void
xQuickSort
(
final
Location
[]
a
,
final
int
first
,
final
int
last
) {
if
(
first
<
last
) {
int
q
=
xPartition
(
a
,
first
,
last
);
// pivot
xQuickSort
(
a
,
first
,
q
-
1
);
// Left
xQuickSort
(
a
,
q
+
1
,
last
);
// Right
}
}
/**
* yQuickSort function: //y-axis Quick Sorting.
*
* @param a (IN Parameter) array of points <br>
* @param first (IN Parameter) first point <br>
* @param last (IN Parameter) last point <br>
*/
public
void
yQuickSort
(
final
Location
[]
a
,
final
int
first
,
final
int
last
) {
if
(
first
<
last
) {
int
q
=
yPartition
(
a
,
first
,
last
);
// pivot
yQuickSort
(
a
,
first
,
q
-
1
);
// Left
yQuickSort
(
a
,
q
+
1
,
last
);
// Right
}
}
/**
* closestPair function: find closest pair.
*
* @param a (IN Parameter) array stored before divide <br>
* @param indexNum (IN Parameter) number coordinates divideArray <br>
* @return minimum distance <br>
*/
public
double
closestPair
(
final
Location
[]
a
,
final
int
indexNum
) {
Location
[]
divideArray
=
new
Location
[
indexNum
];
System
.
arraycopy
(
a
,
0
,
divideArray
,
0
,
indexNum
);
// Copy previous array
int
divideX
=
indexNum
/
2
;
// Intermediate value for divide
Location
[]
leftArray
=
new
Location
[
divideX
];
// divide - left array
// divide-right array
Location
[]
rightArray
=
new
Location
[
indexNum
-
divideX
];
if
(
indexNum
<=
3
) {
// If the number of coordinates is 3 or less
return
bruteForce
(
divideArray
);
}
// divide-left array
System
.
arraycopy
(
divideArray
,
0
,
leftArray
,
0
,
divideX
);
// divide-right array
System
.
arraycopy
(
divideArray
,
divideX
,
rightArray
,
0
,
indexNum
-
divideX
);
double
minLeftArea
=
0
;
// Minimum length of left array
double
minRightArea
=
0
;
// Minimum length of right array
double
minValue
=
0
;
// Minimum lengt
minLeftArea
=
closestPair
(
leftArray
,
divideX
);
// recursive closestPair
minRightArea
=
closestPair
(
rightArray
,
indexNum
-
divideX
);
// window size (= minimum length)
minValue
=
Math
.
min
(
minLeftArea
,
minRightArea
);
// Create window. Set the size for creating a window
// and creating a new array for the coordinates in the window
for
(
int
i
=
0
;
i
<
indexNum
;
i
++) {
double
xGap
=
Math
.
abs
(
divideArray
[
divideX
].
x
-
divideArray
[
i
].
x
);
if
(
xGap
<
minValue
) {
ClosestPair
.
setSecondCount
(
secondCount
+
1
);
// size of the array
}
else
{
if
(
divideArray
[
i
].
x
>
divideArray
[
divideX
].
x
) {
break
;
}
}
}
// new array for coordinates in window
Location
[]
firstWindow
=
new
Location
[
secondCount
];
int
k
=
0
;
for
(
int
i
=
0
;
i
<
indexNum
;
i
++) {
double
xGap
=
Math
.
abs
(
divideArray
[
divideX
].
x
-
divideArray
[
i
].
x
);
if
(
xGap
<
minValue
) {
// if it's inside a window
firstWindow
[
k
] =
divideArray
[
i
];
// put in an array
k
++;
}
else
{
if
(
divideArray
[
i
].
x
>
divideArray
[
divideX
].
x
) {
break
;
}
}
}
yQuickSort
(
firstWindow
,
0
,
secondCount
-
1
);
// Sort by y coordinates
/* Coordinates in Window */
double
length
=
0
;
// size comparison within window
for
(
int
i
=
0
;
i
<
secondCount
-
1
;
i
++) {
for
(
int
j
= (
i
+
1
);
j
<
secondCount
;
j
++) {
double
xGap
=
Math
.
abs
(
firstWindow
[
i
].
x
-
firstWindow
[
j
].
x
);
double
yGap
=
Math
.
abs
(
firstWindow
[
i
].
y
-
firstWindow
[
j
].
y
);
if
(
yGap
<
minValue
) {
length
=
Math
.
sqrt
(
Math
.
pow
(
xGap
,
2
) +
Math
.
pow
(
yGap
,
2
));
// If measured distance is less than current min distance
if
(
length
<
minValue
) {
// Change minimum distance to current distance
minValue
=
length
;
// Conditional for registering final coordinate
if
(
length
<
minNum
) {
ClosestPair
.
setMinNum
(
length
);
point1
=
firstWindow
[
i
];
point2
=
firstWindow
[
j
];
}
}
}
else
{
break
;
}
}
}
ClosestPair
.
setSecondCount
(
0
);
return
minValue
;
}
/**
* bruteForce function: When the number of coordinates is less than 3.
*
* @param arrayParam (IN Parameter) array stored before divide <br>
* @return <br>
*/
public
double
bruteForce
(
final
Location
[]
arrayParam
) {
double
minValue
=
Double
.
MAX_VALUE
;
// minimum distance
double
length
=
0
;
double
xGap
=
0
;
// Difference between x coordinates
double
yGap
=
0
;
// Difference between y coordinates
double
result
=
0
;
if
(
arrayParam
.
length
==
2
) {
// Difference between x coordinates
xGap
= (
arrayParam
[
0
].
x
-
arrayParam
[
1
].
x
);
// Difference between y coordinates
yGap
= (
arrayParam
[
0
].
y
-
arrayParam
[
1
].
y
);
// distance between coordinates
length
=
Math
.
sqrt
(
Math
.
pow
(
xGap
,
2
) +
Math
.
pow
(
yGap
,
2
));
// Conditional statement for registering final coordinate
if
(
length
<
minNum
) {
ClosestPair
.
setMinNum
(
length
);
}
point1
=
arrayParam
[
0
];
point2
=
arrayParam
[
1
];
result
=
length
;
}
if
(
arrayParam
.
length
==
3
) {
for
(
int
i
=
0
;
i
<
arrayParam
.
length
-
1
;
i
++) {
for
(
int
j
= (
i
+
1
);
j
<
arrayParam
.
length
;
j
++) {
// Difference between x coordinates
xGap
= (
arrayParam
[
i
].
x
-
arrayParam
[
j
].
x
);
// Difference between y coordinates
yGap
= (
arrayParam
[
i
].
y
-
arrayParam
[
j
].
y
);
// distance between coordinates
length
=
Math
.
sqrt
(
Math
.
pow
(
xGap
,
2
) +
Math
.
pow
(
yGap
,
2
));
// If measured distance is less than current min distance
if
(
length
<
minValue
) {
// Change minimum distance to current distance
minValue
=
length
;
if
(
length
<
minNum
) {
// Registering final coordinate
ClosestPair
.
setMinNum
(
length
);
point1
=
arrayParam
[
i
];
point2
=
arrayParam
[
j
];
}
}
}
}
result
=
minValue
;
}
return
result
;
// If only one point returns 0.
}
/**
* main function: execute class.
*
* @param args (IN Parameter) <br>
* @throws IOException If an input or output exception occurred
*/
public
static
void
main
(
final
String
[]
args
) {
// Input data consists of one x-coordinate and one y-coordinate
ClosestPair
cp
=
new
ClosestPair
(
12
);
cp
.
array
[
0
] =
cp
.
buildLocation
(
2
,
3
);
cp
.
array
[
1
] =
cp
.
buildLocation
(
2
,
16
);
cp
.
array
[
2
] =
cp
.
buildLocation
(
3
,
9
);
cp
.
array
[
3
] =
cp
.
buildLocation
(
6
,
3
);
cp
.
array
[
4
] =
cp
.
buildLocation
(
7
,
7
);
cp
.
array
[
5
] =
cp
.
buildLocation
(
19
,
4
);
cp
.
array
[
6
] =
cp
.
buildLocation
(
10
,
11
);
cp
.
array
[
7
] =
cp
.
buildLocation
(
15
,
2
);
cp
.
array
[
8
] =
cp
.
buildLocation
(
15
,
19
);
cp
.
array
[
9
] =
cp
.
buildLocation
(
16
,
11
);
cp
.
array
[
10
] =
cp
.
buildLocation
(
17
,
13
);
cp
.
array
[
11
] =
cp
.
buildLocation
(
9
,
12
);
System
.
out
.
println
(
"Input data"
);
System
.
out
.
println
(
"Number of points: "
+
cp
.
array
.
length
);
for
(
int
i
=
0
;
i
<
cp
.
array
.
length
;
i
++) {
System
.
out
.
println
(
"x: "
+
cp
.
array
[
i
].
x
+
", y: "
+
cp
.
array
[
i
].
y
);
}
cp
.
xQuickSort
(
cp
.
array
,
0
,
cp
.
array
.
length
-
1
);
// Sorting by x value
double
result
;
// minimum distance
result
=
cp
.
closestPair
(
cp
.
array
,
cp
.
array
.
length
);
// ClosestPair start
// minimum distance coordinates and distance output
System
.
out
.
println
(
"Output Data"
);
System
.
out
.
println
(
"("
+
cp
.
point1
.
x
+
", "
+
cp
.
point1
.
y
+
")"
);
System
.
out
.
println
(
"("
+
cp
.
point2
.
x
+
", "
+
cp
.
point2
.
y
+
")"
);
System
.
out
.
println
(
"Minimum Distance : "
+
result
);
}
}
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