leetcode-[3]Max Points on a Line

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

思路：最多的點，必然是點連成線時，所有斜率相同的最多的組合情況；

　　   那麼如果不在同一直線點的組合也可能斜率相同，找其中一點與其它點連即可。

#include <iostream>#include <vector>#include <map>using namespace std;struct Point {    int x;    int y;    Point(): x(0), y(0) {}    Point(int a, int b): x(a), y(b) {}};class Solution {public:    int maxPoints(vector<Point> &points) {        if (points.size() < 2)            return points.size();        int result = 0;        for (int i = 0; i < points.size(); i++) {            map<pair<int, int>, int> line;            int overlap = 0, vertical = 0, curMax = 0;            for (int j = i + 1; j < points.size(); j++)    {                if((points[i].x == points[j].x) &&                    (points[i].y == points[j].y)) {                    overlap ++;                    continue;                }                else if (points[i].x == points[j].x) {                    vertical ++;                }                else {                    int dx = points[i].x - points[j].x;                        int dy = points[i].y - points[j].y;                        int gcd = GCD(dx, dy);                        dx /= gcd;                    dy /= gcd;                                        line[make_pair(dx, dy)]++;                    curMax = max(line[make_pair(dx, dy)], curMax);                    }                curMax = max(vertical, curMax);            }            result = max(result, curMax+overlap+1);        }                return result;    }    int GCD(int a, int b) {        if (b == 0)            return a;        return GCD(b, a%b);    }};int main() {    vector<Point> points;    points.push_back(Point(3, 4));    points.push_back(Point(3, 4));    points.push_back(Point(3, 4));    Solution *solution = new Solution();    cout << solution->maxPoints(points) << endl;    // (3,10),(0,2),(0,2),(3,10)    vector<Point> points2;        points2.push_back(Point(3, 10));    points2.push_back(Point(0, 2));    points2.push_back(Point(0, 2));    points2.push_back(Point(3, 10));    cout << solution->maxPoints(points2) << endl;        return 0;}

 

leetcode-[3]Max Points on a Line