ClosestPair
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SeonJae
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ClosestPair/ClosestPair.java
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211
ClosestPair/ClosestPair.java
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import java.io.*;
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import java.util.*;
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public class ClosestPair {
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static int count = 0;// array length
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static int secondCount = 0;// array length
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static Location array[] = new Location[10000];
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static Location point1 = null; // Minimum point coordinate
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static Location point2 = null; // Minimum point coordinate
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static double minNum = Double.MAX_VALUE;// Minimum point length
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private static class Location { // Location class
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double x = 0, y = 0;
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public Location(double x, double y) { //Save x, y coordinates
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this.x = x;
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this.y = y;
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}
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}
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public static int xPartition(Location[] a, int first, int last) { // x-axis Quick Sorting
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Location pivot = a[last]; // pivot
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int pIndex = last;
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int i = first - 1;
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Location temp; // Temporarily store the value for position transformation
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for (int j = first; j <= last - 1; j++) {
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if (a[j].x <= pivot.x) { // Less than or less than pivot
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i++;
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temp = a[i]; // array[i] <-> array[j]
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a[i] = a[j];
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a[j] = temp;
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}
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}
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i++;
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temp = a[i];// array[pivot] <-> array[i]
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a[i] = a[pIndex];
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a[pIndex] = temp;
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return i;// pivot index
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}
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public static int yPartition(Location[] a, int first, int last) { //y-axis Quick Sorting
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Location pivot = a[last]; // pivot
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int pIndex = last;
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int i = first - 1;
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Location temp; // Temporarily store the value for position transformation
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for (int j = first; j <= last - 1; j++) {
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if (a[j].y <= pivot.y) { // Less than or less than pivot
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i++;
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temp = a[i]; // array[i] <-> array[j]
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a[i] = a[j];
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a[j] = temp;
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}
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}
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i++;
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temp = a[i];// array[pivot] <-> array[i]
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a[i] = a[pIndex];
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a[pIndex] = temp;
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return i;// pivot index
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}
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public static void xQuickSort(Location[] a, int first, int last) { //x-axis Quick Sorting
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if (first < last) {
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int q = xPartition(a, first, last); // pivot
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xQuickSort(a, first, q - 1); // Left
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xQuickSort(a, q + 1, last); // Right
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}
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}
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public static void yQuickSort(Location[] a, int first, int last) { //y-axis Quick Sorting
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if (first < last) {
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int q = yPartition(a, first, last); // pivot
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yQuickSort(a, first, q - 1); // Left
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yQuickSort(a, q + 1, last); // Right
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}
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}
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public static double closestPair(Location[] a, int indexNum, int first, int last) {// closestPair
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Location divideArray[] = new Location[indexNum]; // array stored before divide
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System.arraycopy(a, 0, divideArray, 0, indexNum); // Copy from previous array
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int totalNum = indexNum; // number of coordinates in the divideArray array
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int divideX = indexNum / 2; // Intermediate value for divide
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Location leftArray[] = new Location[divideX]; //divide - left array
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Location rightArray[] = new Location[totalNum - divideX]; //divide - right array
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if (indexNum <= 3) { // If the number of coordinates is 3 or less
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return bruteForce(divideArray);
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}
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System.arraycopy(divideArray, 0, leftArray, 0, divideX); //divide - left array
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System.arraycopy(divideArray, divideX, rightArray, 0, totalNum - divideX); //divide - right array
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double minLeftArea = 0; //Minimum length of left array
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double minRightArea = 0; //Minimum length of right array
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double minValue = 0; //Minimum lengt
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minLeftArea = closestPair(leftArray, divideX, 0, divideX - 1); // recursive closestPair
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minRightArea = closestPair(rightArray, totalNum - divideX, divideX, totalNum - divideX - 1);
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minValue = Math.min(minLeftArea, minRightArea);// window size (= minimum length)
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// Create window
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for (int i = 0; i < totalNum; i++) { // Set the size for creating a window and creating a new array for the coordinates in the window
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double xGap = Math.abs(divideArray[divideX].x - divideArray[i].x);
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if (xGap < minValue) {
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secondCount++; // size of the array
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} else {
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if (divideArray[i].x > divideArray[divideX].x) {
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break;
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}
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}
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}
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Location firstWindow[] = new Location[secondCount]; // new array for coordinates in window
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int k = 0;
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for (int i = 0; i < totalNum; i++) {
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double xGap = Math.abs(divideArray[divideX].x - divideArray[i].x);
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if (xGap < minValue) { // if it's inside a window
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firstWindow[k] = divideArray[i]; // put in an array
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k++;
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} else {
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if (divideArray[i].x > divideArray[divideX].x) {
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break;
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}
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}
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}
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yQuickSort(firstWindow, 0, secondCount - 1);// Sort by y coordinates
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/ * Coordinates in Window * /
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double length = 0;
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for (int i = 0; i < secondCount - 1; i++) { // size comparison within window
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for (int j = (i + 1); j < secondCount; j++) {
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double xGap = Math.abs(firstWindow[i].x - firstWindow[j].x);
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double yGap = Math.abs(firstWindow[i].y - firstWindow[j].y);
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if (yGap < minValue) {
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length = (double) Math.sqrt(Math.pow(xGap, 2) + Math.pow(yGap, 2));
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if (length < minValue) { // If the measured distance is less than the current minimum distance
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minValue = length;// Change minimum distance to current distance
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if (length < minNum) { // Conditional statement for registering final coordinate
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minNum = length;
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point1 = firstWindow[i];
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point2 = firstWindow[j];
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}
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}
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}
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else
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break;
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}
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}
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secondCount = 0;
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return minValue;
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}
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public static double bruteForce(Location[] array) { // When the number of coordinates is less than 3
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double minValue = Double.MAX_VALUE; // minimum distance
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double length = 0;
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double xGap = 0, yGap = 0; // Difference between x, y coordinates
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if (array.length == 2) { // When there are two coordinates
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xGap = (array[0].x - array[1].x); // Difference between x coordinates
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yGap = (array[0].y - array[1].y); // Difference between y coordinates
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length = (double) Math.sqrt(Math.pow(xGap, 2) + Math.pow(yGap, 2)); // distance between coordinates
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if (length < minNum) { // Conditional statement for registering final coordinate
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minNum = length;
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point1 = array[0];
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point2 = array[1];
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}
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return length;
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} else if (array.length == 3) { // When there are 3 coordinates
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for (int i = 0; i < array.length - 1; i++) {
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for (int j = (i + 1); j < array.length; j++) {
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xGap = (array[i].x - array[j].x); // Difference between x coordinates
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yGap = (array[i].y - array[j].y); // Difference between y coordinates
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length = (double) Math.sqrt(Math.pow(xGap, 2) + Math.pow(yGap, 2)); // distance between coordinates
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if (length < minValue) { // If the measured distance is less than the current minimum distance
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minValue = length; // Change minimum distance to current distance
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if (length < minNum) { // Conditional statement for registering final coordinate
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minNum = length;
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point1 = array[i];
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point2 = array[j];
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}
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}
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}
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}
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return minValue;
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}
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return minValue;
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}
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public static void main(String[] args) throws IOException {
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// TODO Auto-generated method stub
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StringTokenizer token;
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BufferedReader in = new BufferedReader(new FileReader("closest_data.txt"));
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//Input data consists of one x-coordinate and one y-coordinate
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String ch;
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System.out.println("Input data");
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while ((ch = in.readLine()) != null) {
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token = new StringTokenizer(ch, " ");
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array[count] = new Location(Double.parseDouble(token.nextToken()), Double.parseDouble(token.nextToken())); // put in an array
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count++; // the number of coordinates actually in the array
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System.out.println("x: "+array[count - 1].x + ", y: " + array[count - 1].y);
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}
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xQuickSort(array, 0, count - 1); // Sorting by x value
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double result; // minimum distance
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result = closestPair(array, count, 0, count - 1); // ClosestPair start
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System.out.println("Output Data");// minimum distance coordinates and distance output
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System.out.println("(" + point1.x + ", " + point1.y + ")");
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System.out.println("(" + point2.x + ", " + point2.y + ")");
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System.out.println("Minimum Distance : " + result);
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}
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}
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12
ClosestPair/closest_data.txt
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12
ClosestPair/closest_data.txt
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@ -0,0 +1,12 @@
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2 3
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2 16
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3 9
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6 3
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7 7
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9 12
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10 11
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15 2
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15 19
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16 11
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17 13
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19 4
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