first commit

collections/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "collections"
+version = "0.1.0"

collections/Cargo.toml

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+[package]
+name = "collections"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

collections/src/main.rs

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+//collections are data structures provided by the standard library that store multiple values. They
+//are more flexible than arrays and tuples, especially when the size or contents of the collectoin
+//are not knows at compile tiem. 
+
+use std::collections::HashMap;
+
+fn main() {
+    //vector
+    let mut numbers = vec![1,2,3];
+    numbers.pop();
+    println!("{:?}", numbers);
+
+    //hasmap
+    let mut scores = HashMap::new();
+    scores.insert("alice", 1);
+    if let Some(s) = scores.get("alice"){ //key is case sensitive 
+        println!("{}", s);
+    }
+
+
+    for val in &numbers{
+        println!("{}", val);
+    }
+}
+
+//when to use what?
+//random access by index = vector
+//fast insertin and removal = vecDeque<T>
+//need sorted keys = BTreeMap<k,v>
+//set of unique items = hasset<t>
+//prioirty queue = BinaryHeap<t>
+