struct Solution {}
impl Solution {
    fn x_diff(a: &[i32], b: &[i32]) -> i32 {
        a[0] - b[0]
    }

    fn y_diff(a: &[i32], b: &[i32]) -> i32 {
        a[1] - b[1]
    }

    pub fn check_straight_line(coordinates: Vec<Vec<i32>>) -> bool {
        assert!(coordinates.len() > 1);

        let (dx, dy) = (
            Solution::x_diff(&coordinates[0], &coordinates[1]),
            Solution::y_diff(&coordinates[0], &coordinates[1]),
        );

        coordinates.iter().all(|pt| {
            dx * Solution::y_diff(pt, &coordinates[0]) == dy * Solution::x_diff(pt, &coordinates[0])
        })
    }
}

fn main() {}

#[cfg(test)]
mod tests {
    use super::*;

    // Input: coordinates = [[1,2],[2,3],[3,4],[4,5],[5,6],[6,7]]
    // Output: true
    #[test]
    fn example_1() {
        assert!(Solution::check_straight_line(vec![
            vec![1, 2],
            vec![2, 3],
            vec![3, 4],
            vec![4, 5],
            vec![5, 6],
            vec![6, 7]
        ]));
    }

    // Input: coordinates = [[1,1],[2,2],[3,4],[4,5],[5,6],[7,7]]
    // Output: false
    #[test]
    fn example_2() {
        assert!(!Solution::check_straight_line(vec![
            vec![1, 1],
            vec![2, 2],
            vec![3, 4],
            vec![4, 5],
            vec![5, 6],
            vec![7, 7]
        ]));
    }
}