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 points.

Example 1:

Input: [[1,1],[-1,1]]
Output: true

Example 2:

Input: [[1,1],[-1,-1]]
Output: false

Follow up: Could you do better than O(n2) ?

解题要点：

用set来记录原始point，然后把x轴里最大最小数相加后，再遍历一遍，新的x用相加后的数字减去x，看这个数在不在set里，如不在，返回False。

class Solution(object):
    def isReflected(self, points):
        """
        :type points: List[List[int]]
        :rtype: bool
        """
        pointSet = set()
        maxNum = -sys.maxint
        minNum = sys.maxint
        for x, y in points:
            maxNum = max(maxNum, x)
            minNum = min(minNum, x)
            pointSet.add((x, y))
        sumNum = maxNum + minNum
        for x, y in points:
            tempTuple = (sumNum - x, y)
            if tempTuple not in pointSet:
                return False
        return True