Li Kou daily question - Day 32 -1232 Dotted line

2022.7.1 Did you brush the questions today ？

subject ：

Given an array  coordinates , among  coordinates[i] = [x, y] , [x, y]  The abscissa is x、 Ordinate for y  The point of . Please judge , Whether these points belong to the same line in the coordinate system .

analysis ：

Here are some two-dimensional arrays , You need to judge whether these two-dimensional arrays are on a straight line , But one thing to pay attention to , If you're going to find out y=kx+b To judge , There will be cases where the denominator is negative when the slope is divided ！

Ideas ： Using the slope formula

(y1-y0)/(x1-x0)=(yi-y0)/(xi-x0)
 Prevention and elimination 0, Transformed into a form of multiplication 
(y1-y0)*(xi-x0)==(x1-x0)*(yi-y0)

analysis ：

1. Violent solution

class Solution {
public:
    bool checkStraightLine(vector<vector<int>>& coordinates) {

        for (auto i = 2; i < coordinates.size(); i++)
        {
            if ((coordinates[1][1]-coordinates[0][1])*(coordinates[i][0]-coordinates[0][0])!=(coordinates[i][1]-coordinates[0][1])*(coordinates[1][0]-coordinates[0][0]))
            {
                return false;
            }
        }
        return true;
    }
};