356. Line Reflection Given n points on a 2D plane, find if there is such a line parallel to y-axis that reflect the given set of points. Example 1: Given points = [[1,1],[-1,1]], return true. Example 2: Given points = [[1,1],[-1,-1]], return false. Follow up: Could you do better than O(n2)? Hint: Find the smallest and largest x-value for all points. If there is a line then it should be at y = (minX + maxX) / 2. For each point, make sure that it has a reflected point in the opposite side. public boolean isReflected(int[][] points) { int min = Integer.MAX_VALUE, max = Integer.MIN_VALUE; Set set = new HashSet(); for (int[] p : points) { set.add(p[0] + "," + p[1]); min = Math.min(min, p[0]); max = Math.max(max, p[0]); } int sum = min + max; for (int[] p : points) { if (!set.contains((sum - p[0]) + "," + p[1])) { return false; } } return true; }