Add problem 3028: Ant on the Boundary

Author: EFanZh

src/lib.rs

@@ -2053,6 +2053,7 @@ pub mod problem_3019_number_of_changing_keys;
 pub mod problem_3021_alice_and_bob_playing_flower_game;
 pub mod problem_3024_type_of_triangle;
 pub mod problem_3026_maximum_good_subarray_sum;
+pub mod problem_3028_ant_on_the_boundary;
 
 #[cfg(test)]
 mod test_utilities;

src/problem_3028_ant_on_the_boundary/mod.rs

@@ -0,0 +1,18 @@
+pub mod prefix_sums;
+
+pub trait Solution {
+    fn return_to_boundary_count(nums: Vec<i32>) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [(&[2, 3, -5] as &[_], 1), (&[3, 2, -3, -4], 0)];
+
+        for (nums, expected) in test_cases {
+            assert_eq!(S::return_to_boundary_count(nums.to_vec()), expected);
+        }
+    }
+}

src/problem_3028_ant_on_the_boundary/prefix_sums.rs

@@ -0,0 +1,33 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn return_to_boundary_count(nums: Vec<i32>) -> i32 {
+        let mut position = 0;
+        let mut result = 0;
+
+        for num in nums {
+            position += num;
+            result += i32::from(position == 0);
+        }
+
+        result
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn return_to_boundary_count(nums: Vec<i32>) -> i32 {
+        Self::return_to_boundary_count(nums)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}