LeetCode 1232. 缀点成线

输入：coordinates = [[1,2],[2,3],[3,4],[4,5],[5,6],[6,7]]
输出：true

输入：coordinates = [[1,1],[2,2],[3,4],[4,5],[5,6],[7,7]]
输出：false
 
提示：
2 <= coordinates.length <= 1000
coordinates[i].length == 2
-10^4 <= coordinates[i][0], coordinates[i][1] <= 10^4
coordinates 中不含重复的点

class Solution {
public:
    bool checkStraightLine(vector<vector<int>>& cd) {
        int dy, dx, i;
        dy = cd[0][1]-cd[1][1];
        dx = cd[0][0]-cd[1][0];
        for(i = 1; i < cd.size(); ++i)
            if(dy*(cd[i][0]-cd[0][0]) != dx*(cd[i][1]-cd[0][1]))
                return false;
        return true;
    }
};