[LeetCode] Max Points on a Line

 1 #include <iostream>
 2 #include <algorithm>
 3 #include <unordered_map>
 4 #include <vector>
 5 #include <limits>
 6 
 7 using namespace std;
 8 
 9 /**
10  * Definition for a point.
11  * struct Point {
12  *     int x;
13  *     int y;
14  *     Point() : x(0), y(0) {}
15  *     Point(int a, int b) : x(a), y(b) {}
16  * };
17  */
18  
19 bool typeisless(const Point &data1,const Point &data2){
20     return data1.x < data2.x;
21 }
22  
23 class Solution {
24 public:
25 
26     int maxPoints(vector<Point> &points) {
27         if(points.size()==0) return 0;
28 
29         int last_x = (points.begin()->x) - 1;
30         int maxnum = INT_MIN,curnum = 0;
31         std::sort(points.begin(),points.end(),typeisless);
32         for(vector<Point>::iterator iter = points.begin();
33             iter != points.end();++iter){
34             if(iter->x == last_x){
35                 ++curnum;
36             }else{
37                 last_x = iter->x;
38                 curnum = 1;
39             }
40 
41             maxnum = maxnum<curnum?curnum:maxnum;
42         }
43 
44         unordered_map<double,int> count_map;
45         count_map.insert(pair<double,int>(0.0,0));
46 
47         for(vector<Point>::iterator iter1 = points.begin();
48             iter1 != points.end();++iter1){
49             count_map.clear();
50             int samepointnum = 0;
51 
52             for(vector<Point>::iterator iter2 = iter1 + 1;
53                 iter2 != points.end();++iter2){
54 
55                 if(iter2->x == iter1->x && iter2->y == iter1->y){
56                    ++samepointnum;continue;
57                 }else if(iter2->x == iter1->x)
58                     continue;
59                 else{
60                     double dslope = (static_cast<double>(iter2->y - iter1->y))/
61                                     (static_cast<double>(iter2->x - iter1->x));
62                     if(count_map.find(dslope) != count_map.end()) ++count_map[dslope];
63                     else{
64                         count_map[dslope] = 1;
65                         ++count_map[dslope];
66                     }
67                 }
68             }
69 
70             for(unordered_map<double,int>::iterator iter=count_map.begin();
71                 iter!=count_map.end();++iter){
72                 if(iter->second + samepointnum > maxnum){
73                     maxnum = iter->second + samepointnum;
74                 }
75             }
76         }
77 
78         return maxnum;
79     }
80 };