Create KClosestPointstoOrigin.java

Leetcode/KClosestPointstoOrigin.java

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+/**
+973. K Closest Points to Origin
+Solved
+Medium
+Topics
+Companies
+Given an array of points where points[i] = [xi, yi] represents a point on the X-Y plane and an integer k, return the k closest points to the origin (0, 0).
+
+The distance between two points on the X-Y plane is the Euclidean distance (i.e., √(x1 - x2)2 + (y1 - y2)2).
+
+You may return the answer in any order. The answer is guaranteed to be unique (except for the order that it is in).
+
+ **/
+/** Mys soluion */
+class Solution {
+    public int[][] kClosest(int[][] points, int k) {
+        double[][] a = new double[points.length][2];
+        int[][] out = new int[k][2];
+        for(int i=0;i<points.length;i++){
+            a[i][0] = findDistance(points[i]);
+            a[i][1] = i;
+            System.out.println(a[i][0]+" , "+a[i][1]);
+        }
+        sortbyColumn(a);
+
+        for(int i=0;i<k;i++){
+            out[i]=points[(int)a[i][1]];
+        }
+        return out;
+
+    }
+
+    public void sortbyColumn(double arr[][]){      
+      Arrays.sort(arr, (a,b)->Double.compare(a[0],b[0])); 
+    }
+
+    public double findDistance(int[] a){
+        return Math.pow(Math.pow(a[0],2)+Math.pow(a[1],2),0.5);
+    }
+}
+
+/** best solution */
+class Solution {
+    public int[][] kClosest(int[][] points, int k) {
+        int smallestK = quickSelect(points, 0, points.length - 1, k);
+        return Arrays.copyOfRange(points, 0, smallestK);
+    }
+
+    private int quickSelect(int[][] points, int left, int right, int k) {
+        if (left >= right) {
+            return k;
+        }
+        int l = left, r = right;
+        int pivotIdx = left + (right - left)/2;
+        int pivotDist = getDist(points[pivotIdx]);
+
+        while (l <= r) {
+            while (l <= r && getDist(points[l]) < pivotDist) {
+                l++;
+            }
+            while (l <= r && getDist(points[r]) > pivotDist) {
+                r--;
+            }
+
+            if (l <= r) {
+                swap(points, l++, r--);
+            }
+        }
+
+        if (k <= r) {
+            return quickSelect(points, left, r, k);
+        }
+
+        return quickSelect(points, l, right, k);
+    }
+
+    private void swap(int[][] points, int i, int j) {
+        int[] tmp = points[i];
+        points[i] = points[j];
+        points[j] = tmp;
+    }
+
+    private int getDist(int[] point) {
+        return point[0] * point[0] + point[1] * point[1];
+    }
+}