LeetCode 149. Max Points on a Line

#include <unordered_map>#include <vector>#include <iostream>#include <climits>using namespace std;struct Point {  int x;  int y;  Point() : x(0), y(0) {}  Point(int a, int b) : x(a), y(b) {}};/*  Two caculate two points are on the same line:  (x1, y1), (x2, y2)  We need to cacualte that res = (x1 - x2) / (y1 - y2), push the HashMap[res]++;  However, there are several cases to cacualte res.  1: y1 == y2  --> divisor equals to 0, in this case, we can store INT_MAX as key.  2: x1 == x2 && y1 == y2, duplicate points, we can stop storing it, use a duplicate counter instead.*/int maxPoints(vector<Point>& points) {  unordered_map<float, int> hashMap;  int maxCount = 0;  for(int i = 0; i < points.size(); ++i) {    hashMap.clear();    hashMap[INT_MIN] = 0;    int duplicate = 1;    for(int j = 0; j < points.size(); ++j) {      if(j == i) continue; // skip the same point.      if((points[i].x == points[j].x) && (points[i].y == points[j].y)) {duplicate++; continue;}      else if(points[i].x == points[j].x) {hashMap[INT_MIN]++;}      else {        float k = (float)(points[j].y - points[i].y) / (points[j].x - points[i].x);        hashMap[k]++;      }    }    auto iter = hashMap.begin();    while(iter != hashMap.end()) {      maxCount = max(maxCount, iter->second + duplicate);      iter++;    }  }  return maxCount;}int main(void) {  // contains duplicates.  vector<Point> test_1{Point(1,1), Point(1, 2), Point(1, 1), Point(1, 1)};  cout << maxPoints(test_1) << endl;   // on the same x line.  vector<Point> test_2{Point(1,1), Point(1, 3), Point(1, 4), Point(1, 5)};  cout << maxPoints(test_2) << endl;  // on the same line.  vector<Point> test_3{Point(1,1), Point(2, 2), Point(3, 3), Point(4, 4)};  cout << maxPoints(test_3) << endl;  // on same y line.  vector<Point> test_4{Point(2,1), Point(3, 1), Point(4, 1), Point(5, 1)};  cout << maxPoints(test_4) << endl;  // make a mix.  vector<Point> test_5{Point(2, 2), Point(3, 3), Point(4, 4), Point(3, 1), Point(4, 1), Point(5, 1), Point(1, 3), Point(1, 4), Point(1, 5)};  cout << maxPoints(test_5) << endl;}