# What does input:[] mean? null maybe?

• In my local Eclipse environment. It works good. If the input is null, it can return 0;

But in OJ, i says like following. Anybody knows what does input [] mean? Thank you all.

``````22 / 27 test cases passed.
Submitted: 0 minutes ago
Input:	[]
Output:	2
Expected:	0
``````

here is my java code:

``````public static int maxPoints(Point[] points) {
if (points == null) {
return 0;
} else if (points.length == 1) {
return 1;
} else if (points.length == 2) {
return 2;
}
/**
* <slope,count>
*/
Map<Double, Integer> slopeMap = new HashMap<Double, Integer>();
long infinite = Integer.MAX_VALUE;
double slope;
int maxLines = 1;
int count = 0;
for (int i = 0; i < points.length - 1; i++) {
boolean b = false;
slopeMap.put(0.0, 1);
for (int j = i + 1; j < points.length; j++) {
if (points[i].equals(points[j])) {
if (slopeMap.containsKey(0.0)) {
slopeMap.put(0.0, 1);
}
continue;
}

if (points[i].x == points[j].x) {
slope = infinite;
} else {
slope = 1.0 * (points[j].y - points[i].y) / (points[j].x - points[i].x);
}
if (!slopeMap.containsKey(slope)) {
count = 2;
} else {
count = slopeMap.get(slope) + 1;
}
slopeMap.put(slope, count);
if (count > maxLines) {
maxLines = count;
b = true;
}
}
if (b)
maxLines = maxLines + slopeMap.get(0.0);
else if (slopeMap.get(0.0) > maxLines)
maxLines = slopeMap.get(0.0);
}
/**
*  maxLines = Combination(maxPoints,2)
*  so maxPoints = sqrt(2*maxLines) + 1
*/
return (int) (Math.sqrt(2 * maxLines) + 1);
}``````

• `[]` means the empty set, an array or list with a length of zero. The array isn't null, as suggested by your first `if`, it just has no elements stored in it. In this case, there are no points in the array. Since there are no points, the maximum number of points on a line is zero.

• Thank you very much. You are right. I overlooked this case.

• please ignore the code above.

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