From 79833af30e82bc258fdf300d5c6701e39ffc95da Mon Sep 17 00:00:00 2001
From: Jordan Gong <jordan.gong@protonmail.com>
Date: Mon, 31 Aug 2020 17:17:31 +0800
Subject: Store data in different way

---
 collections/src/main.rs | 167 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 167 insertions(+)
 create mode 100644 collections/src/main.rs

(limited to 'collections/src/main.rs')

diff --git a/collections/src/main.rs b/collections/src/main.rs
new file mode 100644
index 0000000..0930ce9
--- /dev/null
+++ b/collections/src/main.rs
@@ -0,0 +1,167 @@
+fn main() {
+    // Vector
+    let v: Vec<i32> = Vec::new();
+
+    // Macro
+    let v = vec![1, 2, 3];
+
+    // Update
+    let mut v = Vec::new();
+
+    v.push(5);
+    v.push(6);
+    v.push(7);
+    v.push(8);
+
+    // Free when out of scope
+    {
+        let v = vec![1, 2, 3];
+    }
+
+    // Access
+    let mut v = vec![1, 2, 3, 4, 5];
+
+    let third: &i32 = &v[2];
+    println!("The third element is {}", third);
+
+    match v.get(2) {
+        Some(third) => println!("The third element is {}", third),
+        None => println!("There is no third element."),
+    }
+
+    // immutable borrow
+    // let first = &v[0];
+    let first = v[0];
+
+    v.push(6);
+
+    println!("The first element is: {}", first);
+
+    // Iterating
+    let v = vec![100, 32, 57];
+    for i in &v {
+        println!("{}", i);
+    }
+
+    // Iterating(mutable)
+    let mut v = vec![100, 32, 57];
+    for i in &mut v {
+        *i += 50;
+    }
+
+    // Storing multiple types using enum
+    #[derive(Debug)]
+    enum SpreadSheetCell {
+        Int(i32),
+        Float(f64),
+        Text(String),
+    }
+
+    let row = vec![
+        SpreadSheetCell::Int(3),
+        SpreadSheetCell::Text(String::from("blue")),
+        SpreadSheetCell::Float(10.12),
+    ];
+
+    for (i, cell) in row.iter().enumerate() {
+        println!("Cell {} is {:?}", i, cell);
+    }
+
+    // Push string
+    let mut s = String::from("foo");
+    s.push_str("bar");
+
+    let mut s = String::from("ol");
+    s.push('l');
+
+    // Concatenation
+    let s1 = String::from("tic");
+    let s2 = String::from("tac");
+    let s3 = String::from("toe");
+
+    // take owership of s1, append s2 and s3 to it
+    let s = s1 + "-" + &s2 + "-" + &s3;
+    println!("{}", s);
+
+    let s1 = String::from("tic");
+    let s2 = String::from("tac");
+    let s3 = String::from("toe");
+
+    let s = format!("{}-{}-{}", s1, s2, s3);
+    println!("{}", s);
+
+    // Iterating
+    for char in "你好世界".chars() {
+        println!("{}", char);
+    }
+
+    for byte in "你好世界".bytes() {
+        println!("{}", byte);
+    }
+
+    // Hash map
+    use std::collections::HashMap;
+
+    let mut scores = HashMap::new();
+
+    scores.insert(String::from("Blue"), 10);
+    scores.insert(String::from("Yellow"), 50);
+
+    // Using `collect` method
+    let teams = vec![String::from("Blue"), String::from("Yellow")];
+    let initial_scores = vec![10, 50];
+
+    let mut scores: HashMap<_, _> = teams.into_iter().zip(initial_scores.into_iter()).collect();
+
+    // Owership
+    let field_name = String::from("Favorite color");
+    let field_value = String::from("Blue");
+
+    let mut map = HashMap::new();
+    map.insert(field_name, field_value);
+
+    // field_name and field_value is invaid now
+    // println!("field_name: {}, field_value: {}", field_name, field_value);
+
+    // Access
+    let team_name = String::from("Blue");
+
+    let score = scores.get(&team_name);
+    match score {
+        Some(score) => println!("{}: {}", team_name, score),
+        None => println!("{} not found", team_name),
+    }
+
+    // if let Some(score) = score {
+    //     println!("{}: {}", team_name, score);
+    // } else {
+    //     println!("{} not found", team_name);
+    // }
+
+    for (key, value) in &scores {
+        println!("{}: {}", key, value);
+    }
+
+    // Updating(overwriting)
+    scores.insert(String::from("Blue"), 25);
+
+    println!("{:?}", scores);
+
+    // Updating(insert if not exist)
+    scores.entry(String::from("Red")).or_insert(50);
+    scores.entry(String::from("Blue")).or_insert(50);
+
+    println!("{:?}", scores);
+
+    // Updating(based on old value)
+    let text = "hello world wonderful world";
+
+    let mut map = HashMap::new();
+
+    for word in text.split_whitespace() {
+        let count = map.entry(word).or_insert(0);
+        *count += 1;
+    }
+
+    println!("{:?}", map);
+}
-- 
cgit v1.2.3