# Java 7ms simple solution beats 99%

• ``````public boolean isReflected(int[][] points) {
if (points == null || points.length == 0 || points[0].length != 2) return true;

int maxX = Integer.MIN_VALUE;
int minX = Integer.MAX_VALUE;

for (int[] point : points) {
if (point[0] > maxX) maxX = point[0];
if (point[0] < minX) minX = point[0];
}

final int line = minX + maxX;

Arrays.sort(points, new Comparator<int[]> () {
@Override
public int compare (int[] i1, int[] i2) {
if (i1[0] != i2[0]) return i1[0] - i2[0];
else if (2 * i1[0] > line) {
return i1[1] - i2[1];
} else return i2[1] - i1[1];
}
});

int p1 = 0, p2 = points.length - 1;
while (p1 <= p2) {
if (points[p1][0] + points[p2][0] != line) return false;
if (points[p1][0] * 2 != line && points[p1][1] != points[p2][1]) return false;
while (p1 + 1 < points.length && points[p1][0] == points[p1 + 1][0] && points[p1][1] == points[p1 + 1][1]) p1++;
while (p2 - 1 >= 0 && points[p2][0] == points[p2 -1][0] && points[p2][1] == points[p2 - 1][1]) p2--;
p1++;
p2--;
}

return true;
}
``````

Actually I think this problem is similar as the TwoSum problem... One can also use HashSet to solve this problem.

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