improve split_from

src/misc.rs

@@ -1,16 +1,10 @@
-pub fn split(min: usize, max: usize, x: usize) -> Vec<Vec<usize>> {
+pub fn split_from(min: usize, max: usize, x: usize) -> Vec<Vec<usize>> {
     if min > x || x > max {
         return Vec::new();
     }
-    let index = x - min;
-
-    let collected = (min..=max).collect::<Vec<usize>>();
-    let split = collected.split_at(index);
-    let mut one = split.0.to_vec();
-    one.reverse();
-    let mut two = split.1.to_vec();
-    two.remove(0);
-    vec![one, two]
+    let x_lower = x.checked_sub(1).unwrap_or(min);
+    let x_upper = (x + 1).min(max);
+    vec![(min..=x_lower).rev().collect(), (x_upper..=max).collect()]
 }
 
 #[cfg(test)]
@@ -19,6 +13,6 @@ mod test {
 
     #[test]
     fn split_test() {
-        assert_eq!(split(0, 6, 2), vec![vec![1, 0], vec![3, 4, 5, 6]]);
+        assert_eq!(split_from(0, 6, 2), vec![vec![1, 0], vec![3, 4, 5, 6]]);
     }
 }