[LeetCode OJ] Max Points on a Line

Max Points on a Line

Submission Details

27 / 27 test cases passed.	Status:  Accepted
Runtime: 472 ms	Submitted: 0 minutes ago

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Submitted Code

Language: java

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/**
 * Definition for a point.
 * class Point {
 *     int x;
 *     int y;
 *     Point() { x = 0; y = 0; }
 *     Point(int a, int b) { x = a; y = b; }
 * }
 */
import java.util.HashMap;
import java.util.Map;
 
 
public class Solution {
    public int maxPoints(Point[] points) {
        if (points == null || points.length == 0)
            return 0;
        int N = points.length;
        if (N == 1)
            return 1;
        if (N == 2)
            return 2;
 
        Map<String, Integer> dict = new HashMap<String, Integer>();
        int maxOverall = 0;
        for (int i = 0; i < N - 1; i++) {
            int same = 1;
            int max = 0;
            for (int j = i + 1; j < N; j++) {
 
                int p1x = points[i].x;
                int p1y = points[i].y;
                int p2x = points[j].x;
                int p2y = points[j].y;
 
                if (p1x == p2x && p1y == p2y) {
                    same++;
                    continue;
                }
 
                int A = p2y - p1y;
                int B = p1x - p2x;
 
                int GCD = gcd(A, B);
                if (GCD != 0 && GCD != 1) {
                    A /= GCD;
                    B /= GCD;
                }
                if (A < 0) {
                    A = -A;
                    B = -B;
                }
 
                String key = A + "," + B;
//              System.out.println("round:" + i + " " + key);
                int value = 1;
                if (dict.containsKey(key)) {
                    value += dict.get(key);
                } 
                dict.put(key, value);
                max = max < value  ? value  : max;
            }
            
            max += same;
            maxOverall = maxOverall < max ? max : maxOverall;
            dict.clear();
        }
 
        return maxOverall;
    }
 
    public int gcd(int a, int b) {
        if (b == 0)
            return a;
        return gcd(b, a % b);
    }
}
 

 

 

 

 

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