> For the complete documentation index, see [llms.txt](https://jimmylin1991.gitbook.io/practice-of-algorithm-problems/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jimmylin1991.gitbook.io/practice-of-algorithm-problems/math/1232.-check-if-it-is-a-straight-line.md).

# 1232. Check If It Is a Straight Line

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.

**Example 1:**

![](https://assets.leetcode.com/uploads/2019/10/15/untitled-diagram-2.jpg)

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

**Example 2:**

![](https://assets.leetcode.com/uploads/2019/10/09/untitled-diagram-1.jpg)

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

**Constraints:**

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

```cpp
// Slope check
bool checkStraightLine(vector<vector<int>>& coordinates) { // time: O(n); space: O(1)
    int x0 = coordinates[0][0], y0 = coordinates[0][1], x1 = coordinates[1][0], y1 = coordinates[1][1];
    int dx = x1 - x0, dy = y1 - y0;
    for (int i = 2; i < coordinates.size(); ++i) {
        int diff_x = coordinates[i][0] - x1, diff_y = coordinates[i][1] - y1;
        if (diff_x * dy != diff_y * dx) return false;
    }
    return true;
}
```