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:

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

Constraints:

• 2 <= coordinates.length <= 1000

• coordinates[i].length == 2

• -10^4 <= coordinates[i][0], coordinates[i][1] <= 10^4

• coordinates contains no duplicate point.

// 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;
}