Bin trie nits (#86)

* type nits

* another nit

* added docs

* change type here too

---------

Co-authored-by: Luke Videckis <lukevideckis@gmail.com>
Co-authored-by: Cameron Custer <73217097+cameroncuster@users.noreply.github.com>

Author: lrvideckis

examples/data_structures/binary_trie.rs

@@ -12,7 +12,7 @@ fn main() {
     for _ in 0..q {
         input! {
             t: u8,
-            x: usize,
+            x: u32,
         }
 
         match t {

src/data_structures/binary_trie.rs

@@ -1,9 +1,12 @@
 //! # Binary Trie which can be used as a multiset of integers
 
+/// u32 or u64
+pub type T = u32;
+
 #[derive(Default)]
 struct Node {
     next: [Option<usize>; 2],
-    sub_sz: isize,
+    sub_sz: i32,
 }
 
 /// # Example
@@ -44,10 +47,10 @@ impl BinaryTrie {
     /// # Complexity
     /// - Time: O(log(max_num))
     /// - Space: O(log(max_num))
-    pub fn update(&mut self, num: usize, delta: isize) {
+    pub fn update(&mut self, num: T, delta: i32) {
         let mut v = 0;
-        for i in (0..usize::BITS).rev() {
-            let bit = (num >> i) & 1;
+        for i in (0..T::BITS).rev() {
+            let bit = ((num >> i) & 1) as usize;
             if self.t[v].next[bit].is_none() {
                 self.t[v].next[bit] = Some(self.t.len());
                 self.t.push(Node::default());
@@ -63,14 +66,15 @@ impl BinaryTrie {
     /// # Complexity
     /// - Time: O(log(max_num))
     /// - Space: O(1)
-    pub fn count(&self, num: usize) -> isize {
+    pub fn count(&self, num: T) -> i32 {
         let mut v = 0;
-        for i in (0..usize::BITS).rev() {
-            let bit = (num >> i) & 1;
-            if self.t[v].next[bit].is_none() {
+        for i in (0..T::BITS).rev() {
+            let bit = ((num >> i) & 1) as usize;
+            if let Some(u) = self.t[v].next[bit] {
+                v = u;
+            } else {
                 return 0;
             }
-            v = self.t[v].next[bit].unwrap();
         }
         self.t[v].sub_sz
     }
@@ -80,12 +84,12 @@ impl BinaryTrie {
     /// # Complexity
     /// - Time: O(log(max_num))
     /// - Space: O(1)
-    pub fn min_xor(&self, num: usize) -> usize {
-        assert!(self.t.len() > 1);
+    pub fn min_xor(&self, num: T) -> T {
+        assert!(self.t[0].sub_sz > 0);
         let mut v = 0;
         let mut ans = 0;
-        for i in (0..usize::BITS).rev() {
-            let bit = (num >> i) & 1;
+        for i in (0..T::BITS).rev() {
+            let bit = ((num >> i) & 1) as usize;
             if self.t[v].next[bit].is_some() && self.t[self.t[v].next[bit].unwrap()].sub_sz > 0 {
                 v = self.t[v].next[bit].unwrap();
             } else {

src/data_structures/trie.rs

@@ -6,7 +6,7 @@ const FIRST_CHAR: usize = 'A' as usize;
 #[derive(Default)]
 struct Node {
     next: [Option<usize>; ALPHABET_SIZE],
-    cnt_words: usize,
+    cnt_words: i32,
 }
 
 /// # Example
@@ -60,7 +60,7 @@ impl Trie {
     /// # Complexity
     /// - Time: O(|s|)
     /// - Space: O(1)
-    pub fn find(&self, s: &[char]) -> usize {
+    pub fn find(&self, s: &[char]) -> i32 {
         let mut v = 0;
         for &ch in s {
             let idx = ch as usize - FIRST_CHAR;