max-points-on-a-line—

max-points-on-a-line——穷举

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

找出二维平面上处于同一条直线上的最大点数

PS： map用法。for(auto pair:slopes）pair.second

 1 /**
 2  * Definition for a point.
 3  * struct Point {
 4  *     int x;
 5  *     int y;
 6  *     Point() : x(0), y(0) {}
 7  *     Point(int a, int b) : x(a), y(b) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     int maxPoints(vector<Point> &points) {
13         int len = points.size();
14         map<float,int> slopes;
15         int res=0;
16         for(int i=0;i<len;i++){
17             slopes.clear();
18             int duplicate=1;
19             for(int j=i+1;j<len;j++){
20                 if(points[i].x==points[j].x&&points[i].y==points[j].y){
21                     duplicate++;
22                 }
23                 else{
24                     float temp= points[i].x==points[j].x? INT_MAX :(float)(points[i].y-points[j].y)/(points[i].x-points[j].x);
25                     slopes[temp]++;
26                 }
27                 
28             }
29             res=max(res,duplicate);
30             for(auto pair:slopes){
31                 res=max(res,pair.second+duplicate);
32             }
33         }
34         return res;
35     }
36 };