diff --git a/divideconquer/ClosestPair.java b/divideconquer/ClosestPair.java new file mode 100644 index 00000000..93a5d164 --- /dev/null +++ b/divideconquer/ClosestPair.java @@ -0,0 +1,348 @@ +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; + /** 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
+ * @param ypar (IN Parameter) y coordinate
+ */ + + 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
+ * @param first (IN Parameter) first point
+ * @param last (IN Parameter) last point
+ * @return pivot index + */ + + public int xPartition( + final Location[] a, final int first, final int last) { + + Location pivot = a[last]; // pivot + int pIndex = last; + 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[pIndex]; + a[pIndex] = temp; + return i; // pivot index + } + + /** yPartition function: arrange y-axis. + * @param a (IN Parameter) array of points
+ * @param first (IN Parameter) first point
+ * @param last (IN Parameter) last point
+ * @return pivot index + */ + + public int yPartition( + final Location[] a, final int first, final int last) { + + Location pivot = a[last]; // pivot + int pIndex = last; + 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[pIndex]; + a[pIndex] = temp; + return i; // pivot index + } + + /** xQuickSort function: //x-axis Quick Sorting. + * @param a (IN Parameter) array of points
+ * @param first (IN Parameter) first point
+ * @param last (IN Parameter) last point
+ */ + + 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
+ * @param first (IN Parameter) first point
+ * @param last (IN Parameter) last point
+ */ + + 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
+ * @param indexNum (IN Parameter) number coordinates divideArray
+ * @return minimum distance
+ */ + + 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 totalNum = indexNum; // number of coordinates in the divideArray + int divideX = indexNum / 2; // Intermediate value for divide + Location[] leftArray = new Location[divideX]; //divide - left array + //divide-right array + Location[] rightArray = new Location[totalNum - 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, totalNum - 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, totalNum - 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 < totalNum; i++) { + double xGap = Math.abs(divideArray[divideX].x - divideArray[i].x); + if (xGap < minValue) { + secondCount++; // 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 < totalNum; 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) { + minNum = length; + point1 = firstWindow[i]; + point2 = firstWindow[j]; + } + } + } + else { + break; + } + } + } + secondCount = 0; + return minValue; + } + + /** bruteForce function: When the number of coordinates is less than 3. + * @param arrayParam (IN Parameter) array stored before divide
+ * @return
+ */ + + 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) { + minNum = 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 + minNum = 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)
+ * @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