# 【LeetCode】 1232. Check If It Is a Straight Line

## Description
> You are given an array `coordinates`, `coordinates[i] = [x, y]`, where `[x, y]` represents the coordinate of a point. Check if these points make a straight line in the XY plane.

> Constraints:
> * `2 <= coordinates.length <= 1000`
> * `coordinates[i].length == 2`
> * `-10^4 <= coordinates[i][0], coordinates[i][1] <= 10^4`
> * `coordinates` contains no duplicate point.

> 給你一個陣列`coordinates`，且`coordinates[i] = [x, y]`，其中`[x, y]`代表一個點座標。檢查這些點是否在XY平面上形成一條直線。

> 限制：
> * `2 <= coordinates.length <= 1000`
> * `coordinates[i].length == 2`
> * `-10^4 <= coordinates[i][0], coordinates[i][1] <= 10^4`
> * `coordinates` 不會有重複的點。

## Example:

Example 1:

Input: coordinates = [[1,2],[2,3],[3,4],[4,5],[5,6],[6,7]]
Output: true


Example 2:

Input: coordinates = [[1,1],[2,2],[3,4],[4,5],[5,6],[7,7]]
Output: false


## Solution

* 檢查斜率是否一致即可(Y的變化量 / X的變化量)。
* 我下面的code不小心把X和Y用反，但其實沒差。
* 然後要注意分母為零的情況，改為確認分母都是一樣的值即可。

### Code

class Solution {
public:
    bool checkStraightLine(vector<vector<int>>& coordinates) {
        if(coordinates[0][1] - coordinates[1][1] == 0)
        {
            for(int i = 2; i < coordinates.size(); i++)
            {
                if((coordinates[0][1] - coordinates[i][1]) != 0)
                    return false;
            }
            return true;
        }
        double radio = (double)(coordinates[0][0] - coordinates[1][0]) / 
                       (coordinates[0][1] - coordinates[1][1]);
        cout << radio;
        for(int i = 2; i < coordinates.size(); i++)
        {
            if((double)(coordinates[0][0] - coordinates[i][0]) / 
                       (coordinates[0][1] - coordinates[i][1]) != radio)
                return false;
        }
        return true;
    }
};

###### tags: `LeetCode` `C++`