diff --git a/src/assignments/assignment10/labyrinth.rs b/src/assignments/assignment10/labyrinth.rs
index 5829748..c0ebcd4 100644
--- a/src/assignments/assignment10/labyrinth.rs
+++ b/src/assignments/assignment10/labyrinth.rs
@@ -18,7 +18,12 @@ pub struct Husband {
 impl Husband {
     /// What might a husband, who is looking for his wife's ID my_wife, be thinking?
     pub fn seeking(my_wife: usize) -> Self {
-        todo!()
+        let mut brain = [usize::MAX; 100];
+        brain[0] = my_wife;
+
+        Self {
+            brain: RefCell::new(brain),
+        }
     }
 
     #[allow(missing_docs)]
@@ -29,7 +34,12 @@ impl Husband {
     /// Based on the information about currently visited room number and someone's wife ID trapped
     /// inside, what the husband should do next?
     pub fn carefully_checks_whos_inside(&self, room: usize, wife: usize) {
-        todo!()
+        *self
+            .brain
+            .borrow_mut()
+            .iter_mut()
+            .find(|brain| **brain == usize::MAX)
+            .unwrap() = wife;
     }
 }
 
@@ -43,6 +53,12 @@ impl Iterator for Strategy<'_> {
     type Item = usize;
 
     fn next(&mut self) -> Option<Self::Item> {
-        todo!()
+        self.husband
+            .brain
+            .borrow()
+            .iter()
+            .rev()
+            .find(|brain| **brain != usize::MAX)
+            .copied()
     }
 }
diff --git a/src/assignments/assignment10/small_exercises.rs b/src/assignments/assignment10/small_exercises.rs
index 9ce49c1..2eca4cb 100644
--- a/src/assignments/assignment10/small_exercises.rs
+++ b/src/assignments/assignment10/small_exercises.rs
@@ -1,6 +1,6 @@
 //! Small exercises.
 
-use std::collections::HashSet;
+use std::{collections::HashSet, f64::consts::SQRT_2};
 
 use itertools::*;
 
@@ -17,7 +17,17 @@ use itertools::*;
 ///
 /// Consult <https://en.wikipedia.org/wiki/Inversion_(discrete_mathematics)> for more details of inversion.
 pub fn inversion<T: Ord>(inner: Vec<T>) -> Vec<(usize, usize)> {
-    todo!()
+    let mut result = vec![];
+
+    for i in 0..inner.len() {
+        for j in i..inner.len() {
+            if inner[i] > inner[j] {
+                result.push((i, j));
+            }
+        }
+    }
+
+    result
 }
 
 /// Represents a node of tree data structure.
@@ -68,7 +78,22 @@ pub enum Node<T> {
 ///
 /// is `1 -> 2 -> 5 -> 6 -> 3 -> 4 -> 7 -> 8 -> 9`.
 pub fn traverse_preorder<T>(root: Node<T>) -> Vec<T> {
-    todo!()
+    let mut result = vec![];
+
+    fn helper<T>(result: &mut Vec<T>, node: Node<T>) {
+        match node {
+            Node::Leaf(v) => result.push(v),
+            Node::NonLeaf((v, nodes)) => {
+                result.push(v);
+                for node in nodes {
+                    helper(result, node);
+                }
+            }
+        }
+    }
+
+    helper(&mut result, root);
+    result
 }
 
 /// File
@@ -114,7 +139,31 @@ pub enum File {
 /// Output: `[("a1", 1), ("a2", 3), ("b1", 3), ("a", 4), ("c", 8), ("b2", 15), ("b", 18), ("root",
 /// 30)]`
 pub fn du_sort(root: &File) -> Vec<(&str, usize)> {
-    todo!()
+    let mut result: Vec<(&str, usize)> = vec![];
+
+    fn helper<'a>(result: &mut Vec<(&'a str, usize)>, file: &'a File) -> usize {
+        match file {
+            File::Data(name, size) => {
+                result.push((name, *size));
+                *size
+            }
+            File::Directory(name, files) => {
+                let mut total_size = 0;
+                for file in files {
+                    total_size += helper(result, file);
+                }
+                result.push((name, total_size));
+                total_size
+            }
+        }
+    }
+    let _ = helper(&mut result, root);
+
+    result.sort_by(|(n1, s1), (n2, s2)| match s1.cmp(s2) {
+        std::cmp::Ordering::Equal => n1.cmp(n2),
+        r => r,
+    });
+    result
 }
 
 /// Remove all even numbers inside a vector using the given mutable reference.
@@ -129,7 +178,17 @@ pub fn du_sort(root: &File) -> Vec<(&str, usize)> {
 /// ```
 #[allow(clippy::ptr_arg)]
 pub fn remove_even(inner: &mut Vec<i64>) {
-    todo!()
+    let mut indices = vec![];
+
+    for (i, v) in inner.iter().enumerate() {
+        if v % 2 == 0 {
+            indices.push(i);
+        }
+    }
+
+    for &i in indices.iter().rev() {
+        let _ = inner.remove(i);
+    }
 }
 
 /// Remove all duplicate occurences of a number inside the array.
@@ -146,7 +205,20 @@ pub fn remove_even(inner: &mut Vec<i64>) {
 /// ```
 #[allow(clippy::ptr_arg)]
 pub fn remove_duplicate(inner: &mut Vec<i64>) {
-    todo!()
+    let mut set = HashSet::new();
+    let mut indices = vec![];
+
+    for (i, v) in inner.iter().enumerate() {
+        if set.contains(v) {
+            indices.push(i);
+        } else {
+            let _ = set.insert(*v);
+        }
+    }
+
+    for &i in indices.iter().rev() {
+        let _ = inner.remove(i);
+    }
 }
 
 /// Returns the natural join of two tables using the first column as the join argument.
@@ -172,15 +244,32 @@ pub fn remove_duplicate(inner: &mut Vec<i64>) {
 ///  20231234 |    Mike   |     ME
 /// ```
 pub fn natural_join(table1: Vec<Vec<String>>, table2: Vec<Vec<String>>) -> Vec<Vec<String>> {
-    todo!()
+    let mut result = vec![];
+
+    for row1 in &table1 {
+        for row2 in &table2 {
+            if row1[0] == row2[0] {
+                let mut temp = vec![];
+                temp.append(&mut row1.clone());
+                temp.extend_from_slice(&row2[1..]);
+
+                result.push(temp);
+            }
+        }
+    }
+
+    result
 }
 
 /// You can freely add more fields.
-struct Pythagorean;
+struct Pythagorean {
+    a: u64,
+    c: u64,
+}
 
 impl Pythagorean {
     fn new() -> Self {
-        todo!()
+        Pythagorean { a: 3, c: 5 }
     }
 }
 
@@ -188,7 +277,44 @@ impl Iterator for Pythagorean {
     type Item = (u64, u64, u64);
 
     fn next(&mut self) -> Option<Self::Item> {
-        todo!()
+        fn gcd(lhs: u64, rhs: u64) -> u64 {
+            let (mut a, mut b) = if lhs >= rhs { (lhs, rhs) } else { (rhs, lhs) };
+
+            while b != 0 {
+                let r = a % b;
+                a = b;
+                b = r;
+            }
+
+            a
+        }
+
+        loop {
+            let a_max = ((self.c as f64) / SQRT_2).floor() as u64;
+
+            while self.a <= a_max {
+                let b = ((self.c * self.c - self.a * self.a) as f64).sqrt();
+                if b.floor() == b {
+                    let b = b as u64;
+                    if gcd(self.a, gcd(b, self.c)) == 1
+                        && self.a * self.a + b * b == self.c * self.c
+                    {
+                        self.a += 1;
+
+                        if self.a - 1 < b {
+                            return Some((self.a - 1, b, self.c));
+                        } else {
+                            return Some((b, self.a - 1, self.c));
+                        }
+                    }
+                }
+
+                self.a += 1;
+            }
+
+            self.c += 1;
+            self.a = 1;
+        }
     }
 }