#356 - Line Reflection

Medium • View on LeetCode • View on GitHub

Problem Description

Given n points on a 2D plane, find if there is such a line parallel to the y-axis that reflects the given points symmetrically.

In other words, answer whether or not if there exists a line that after reflecting all points over the given line, the original points' set is the same as the reflected ones.

Note that there can be repeated points.

Solution

/**
 * @param {number[][]} points
 * @return {boolean}
 */
var isReflected = function(points) {
  const pointSet = new Set(points.map(([x, y]) => `${x},${y}`));
  let minX = Infinity;
  let maxX = -Infinity;

  for (const [x] of points) {
    minX = Math.min(minX, x);
    maxX = Math.max(maxX, x);
  }

  const sum = minX + maxX;
  for (const [x, y] of points) {
    if (!pointSet.has(`${sum - x},${y}`)) {
      return false;
    }
  }

  return true;
};