【leetcode】Max Points on a Line

题目：Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.

解法：从任意一点开始，找斜率相同的最大点数，用HashMap

代码：

/** * 从任意一点开始，找斜率相同的最大点数 * 特别注意和开始点重点的情况 * @param points * @return */public int maxPoints(Point[] points){HashMap<Float, Integer> slopeMap = new HashMap<Float, Integer>();int size = points.length;if(size == 0 || size == 1)    return size;int maxSlopeTime = 1;for(int i = 0; i < size; i++){slopeMap.clear();int tempMaxSlopeTime = 0;;int duplicate = 1;//表示和第i个点重复的次数for(int j = i + 1; j < size; j++){if(points[i].x == points[j].x && points[i].y == points[j].y){duplicate++;continue;}float dx = points[i].x - points[j].x;float dy = points[i].y - points[j].y;float slope;if(dx == 0.0f)slope = 0.0f;//如果直接用dy/dx，则会有-0.0和0.0两种情况else if(dy == 0.0f)slope = Float.POSITIVE_INFINITY;//如果直接用dy/dx，则会有-infinity和infinity两种情况elseslope = dy/dx;if(slopeMap.containsKey(slope)){slopeMap.put(slope, slopeMap.get(slope) + 1);if(tempMaxSlopeTime < slopeMap.get(slope))tempMaxSlopeTime = slopeMap.get(slope);}else{slopeMap.put(slope, 1);if(tempMaxSlopeTime < 1)tempMaxSlopeTime = 1;}}if(tempMaxSlopeTime + duplicate > maxSlopeTime)maxSlopeTime = tempMaxSlopeTime + duplicate;}return maxSlopeTime;}