max-points-on-a-line
Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.
ret表示垂直x轴线上的点数,dup表示和改点重合的点数。
import java.util.HashMap; import java.util.Map; /** * Definition for a point. * class Point { * int x; * int y; * Point() { x = 0; y = 0; } * Point(int a, int b) { x = a; y = b; } * } */ public class Solution { public int maxPoints(Point[] points){ int n = points.length; if(n<2)return n; int ret = 0; for(int i = 0; i < n; i++){ int dup = 1; int vtl = 0; Map<Float, Integer> map = new HashMap<Float, Integer>(); Point a = points[i]; for(int j = 0; j < n; j++){ if(i == j) continue; Point b = points[j]; if(a.x == b.x){ if(a.y==b.y)dup++; else vtl++; }else{ float k = (float)(a.y-b.y)/(a.x-b.x); if(map.get(k)==null)map.put(k,1); else map.put(k,map.get(k)+1); } } int max = vtl; for(float k:map.keySet()){ max = Math.max(max, map.get(k)); } ret = Math.max(ret, max+dup); } return ret; } }