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rustgym/leetcode/
_469_convex_polygon.rs

1struct Solution;
2
3impl Solution {
4    fn is_convex(points: Vec<Vec<i32>>) -> bool {
5        let n = points.len();
6        let mut positive = 0;
7        let mut negative = 0;
8        for i in 0..n {
9            let sign = Self::cross(&points[i], &points[(i + 1) % n], &points[(i + 2) % n]);
10            if sign >= 0 {
11                positive += 1;
12            }
13            if sign <= 0 {
14                negative += 1;
15            }
16        }
17        positive == n || negative == n
18    }
19
20    fn cross(a: &[i32], b: &[i32], c: &[i32]) -> i32 {
21        (b[0] - a[0]) * (c[1] - b[1]) - (b[1] - a[1]) * (c[0] - b[0])
22    }
23}
24
25#[test]
26fn test() {
27    let points = vec_vec_i32![[0, 0], [0, 1], [1, 1], [1, 0]];
28    let res = true;
29    assert_eq!(Solution::is_convex(points), res);
30    let points = vec_vec_i32![[0, 0], [0, 10], [10, 10], [10, 0], [5, 5]];
31    let res = false;
32    assert_eq!(Solution::is_convex(points), res);
33}