PROBLEM DESCRIPTION
Given an array of points where points[i] = [xi, yi] represents a point on the X-Y plane, return the maximum number of points that lie on the same straight line.
leetcode
SOLUTION
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import java.util.HashMap;
import java.util.Map;
class Solution {
public int maxPoints(int[][] points) {
int maxLength = 1; // Initialize the maximum length of points on the same line to 1 (minimum possible)
for (int i = 0; i < points.length; i++) {
//fix the first point
int[] p1 = points[i];
int x1 = p1[0];
int y1 = p1[1];
// Create a map to store slopes and their counts (with other points)
Map<Double, Integer> map = new HashMap<>();
for (int j = i + 1; j < points.length; j++) {
int[] p2 = points[j];
int x2 = p2[0];
int y2 = p2[1];
double m = 0; // Initialize the slope to 0
if (x1 == x2) {
// If the x-coordinates are the same, the line is vertical (infinite slope)
m = Double.POSITIVE_INFINITY;
} else if (y1 == y2) {
// If the y-coordinates are the same, the line is horizontal (slope is 0)
m = 0;
} else {
// Calculate the slope for non-vertical and non-horizontal lines
m = (double) (y2 - y1) / (x2 - x1);
}
// Store the slope in the map along with its count (how many points share the same slope)
map.put(m, map.getOrDefault(m, 0) + 1);
// Update the maximum length of points on the same line
// We are adding one because the number points will be one more. The HashMap contains frequency for slope x.
maxLength = Math.max(maxLength, map.get(m) + 1);
}
}
return maxLength;
}
}