problems(rs): add „1996. The Number of Weak Characters in the Game“

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/the-number-of-weak-characters-in-the-game.rs

@@ -0,0 +1,125 @@
+#[derive(Debug, PartialEq, Eq)]
+struct Property {
+    attack: i32,
+    defense: i32,
+}
+
+impl Property {
+    fn is_weak(&self, rhs: &Property) -> bool {
+        self.attack < rhs.attack && self.defense < rhs.defense
+    }
+}
+
+impl From<&Vec<i32>> for Property {
+    fn from(v: &Vec<i32>) -> Self {
+        Self {
+            attack: v[0],
+            defense: v[1],
+        }
+    }
+}
+
+impl PartialOrd for Property {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        match self.attack.partial_cmp(&other.attack) {
+            Some(core::cmp::Ordering::Equal) => other.defense.partial_cmp(&self.defense),
+            ord => ord,
+        }
+    }
+}
+
+impl Ord for Property {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        if self.attack != other.attack {
+            self.attack.cmp(&other.attack)
+        } else {
+            other.defense.cmp(&self.defense)
+        }
+    }
+}
+
+struct Acc {
+    max: i32,
+    count: i32,
+}
+
+impl Acc {
+    fn new(m: i32) -> Acc {
+        Acc { max: m, count: 0 }
+    }
+
+    fn update(self, p: &Property) -> Acc {
+        if p.defense < self.max {
+            Acc {
+                max: self.max,
+                count: self.count + 1,
+            }
+        } else {
+            Acc {
+                max: p.defense,
+                count: self.count,
+            }
+        }
+    }
+}
+
+impl Solution {
+    pub fn number_of_weak_characters(properties: Vec<Vec<i32>>) -> i32 {
+        let mut properties: Vec<Property> = properties.iter().map(From::from).collect();
+        properties.sort();
+
+        properties
+            .iter()
+            .rfold(Acc::new(properties.last().unwrap().defense), Acc::update)
+            .count
+    }
+}
+struct Solution {}
+
+fn main() {
+    println!("Hello World!");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_example() {
+        assert_eq!(
+            Solution::number_of_weak_characters(vec![vec![5, 5], vec![6, 3], vec![3, 6]]),
+            0
+        );
+    }
+
+    #[test]
+    fn test_another_example() {
+        assert_eq!(
+            Solution::number_of_weak_characters(vec![vec![2, 2], vec![3, 3]]),
+            1
+        );
+    }
+
+    #[test]
+    fn test_another_another_example() {
+        assert_eq!(
+            Solution::number_of_weak_characters(vec![vec![1, 5], vec![10, 4], vec![4, 3]]),
+            1
+        );
+    }
+
+    #[test]
+    fn test_bigger_example() {
+        assert_eq!(
+            Solution::number_of_weak_characters(vec![
+                vec![1, 5],
+                vec![10, 4],
+                vec![4, 3],
+                vec![2, 6],
+                vec![1, 1],
+                vec![10, 6]
+            ]),
+            3
+        );
+    }
+}