main: add merge_util with k-merge

src/main.rs

@@ -38,6 +38,7 @@ mod i18n_helpers;
 mod gettext_strings;
 mod web;
 mod template_helpers;
+mod merge_util;
 
 fn main() {
     if let Err(e) = web::serve() {

src/merge_util.rs

@@ -0,0 +1,61 @@
+// Blog post: https://creativcoder.dev/merge-k-sorted-arrays-rust
+// Merge k sorted arrays
+
+use std::collections::BinaryHeap;
+use std::cmp::Reverse;
+use std::cmp::Ordering;
+
+#[derive(Debug, Eq)]
+struct Item<'a> {
+    arr: &'a &'a [u32],
+    idx: usize
+}
+
+impl<'a> PartialEq for Item<'a> {
+    fn eq(&self, other: &Self) -> bool {
+        self.get_item() == other.get_item()
+    }
+}
+
+impl<'a> PartialOrd for Item<'a> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        self.get_item().partial_cmp(&other.get_item())
+    }
+}
+
+impl<'a> Ord for Item<'a> {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.get_item().cmp(&other.get_item())
+    }
+}
+
+impl<'a> Item<'a> {
+    fn new(arr: &'a &[u32], idx: usize) -> Self {
+        Self { arr, idx }
+    }
+
+    fn get_item(&self) -> u32 {
+        self.arr[self.idx]
+    }
+}
+
+pub fn merge_vectors(arrays: Vec<&[u32]>) -> Vec<u32> {
+    let mut sorted = Vec::with_capacity(arrays.iter().map(|a| a.len()).sum());
+
+    let mut heap = BinaryHeap::with_capacity(arrays.len());
+    for arr in &arrays {
+        let item = Item::new(arr, 0);
+        heap.push(Reverse(item));
+    }
+
+    while !heap.is_empty() {
+        let mut it = heap.pop().unwrap();
+        sorted.push(it.0.get_item());
+        it.0.idx += 1;
+        if it.0.idx < it.0.arr.len() {
+            heap.push(it)
+        }
+    }
+
+    sorted
+}