Add problem 2222: Number of Ways to Select Buildings

src/lib.rs

@@ -1576,6 +1576,7 @@ pub mod problem_2210_count_hills_and_valleys_in_an_array;
 pub mod problem_2215_find_the_difference_of_two_arrays;
 pub mod problem_2216_minimum_deletions_to_make_array_beautiful;
 pub mod problem_2220_minimum_bit_flips_to_convert_number;
+pub mod problem_2222_number_of_ways_to_select_buildings;
 pub mod problem_2224_minimum_number_of_operations_to_convert_time;
 pub mod problem_2225_find_players_with_zero_or_one_losses;
 pub mod problem_2226_maximum_candies_allocated_to_k_children;

src/problem_2222_number_of_ways_to_select_buildings/dynamic_programming.rs

@@ -0,0 +1,43 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn number_of_ways(s: String) -> i64 {
+        let mut zero = 0_u32;
+        let mut one_zero = 0_u32;
+        let mut one = 0_u32;
+        let mut zero_one = 0_u32;
+
+        s.into_bytes().into_iter().fold(0_u64, |result, c| {
+            result
+                + u64::from(if c == b'0' {
+                    zero += 1;
+                    one_zero += one;
+
+                    zero_one
+                } else {
+                    one += 1;
+                    zero_one += zero;
+
+                    one_zero
+                })
+        }) as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn number_of_ways(s: String) -> i64 {
+        Self::number_of_ways(s)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_2222_number_of_ways_to_select_buildings/dynamic_programming_2.rs

@@ -0,0 +1,34 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn number_of_ways(s: String) -> i64 {
+        let mut states = [(0_u32, 0_u32), (0_u32, 0_u32)];
+
+        s.into_bytes().into_iter().fold(0_u64, |result, c| {
+            let c = usize::from(c & 1);
+
+            states[c].0 += 1;
+            states[c].1 += states[1 - c].0;
+
+            result + u64::from(states[1 - c].1)
+        }) as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn number_of_ways(s: String) -> i64 {
+        Self::number_of_ways(s)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_2222_number_of_ways_to_select_buildings/mod.rs

@@ -0,0 +1,19 @@
+pub mod dynamic_programming;
+pub mod dynamic_programming_2;
+
+pub trait Solution {
+    fn number_of_ways(s: String) -> i64;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [("001101", 6), ("11100", 0)];
+
+        for (s, expected) in test_cases {
+            assert_eq!(S::number_of_ways(s.to_string()), expected);
+        }
+    }
+}