Added vectors file

Author: hitesh-bhatnagar

examples/06_vectors.rs

@@ -0,0 +1,171 @@
+use std::string;
+
+fn main() {
+    // PART 1 -> Creating a Vec
+
+    // Method 1 - empty Vec, type must be specified
+    let mut nums: Vec<i32> = Vec::new();
+    println!("empty vec: {:?}", nums);
+
+    // Method 2 - vec! macro, type is inferred
+    let scores = vec![10, 20, 30, 40, 50];
+    println!("Scores: {:?}", scores);
+
+    // Method 3: vec of strings
+    let names = vec![
+        String::from("alice"),
+        String::from("bob"),
+        String::from("charlie"),
+    ];
+
+    println!("names: {:?}", names);
+
+    // PART 2: Adding & Removing Items
+
+    let mut fruits = Vec::new();
+
+    //push -- add to the END
+    fruits.push("apple");
+    fruits.push("banana");
+    fruits.push("cranberries");
+    println!("after push : {:?}", fruits);
+
+    // pop -- remove from the END, returns Option
+    let last = fruits.pop();
+    match last {
+        Some(f) => println!("popped: {}", f),
+        None => println!("vec was empty"),
+    }
+
+    println!("after pop: {:?}", fruits);
+
+    fruits.insert(1, "mango");
+    println!("after insert at 1: {:?}", fruits);
+
+    // remove --> remove at a specific index, returns the value
+    let removed = fruits.remove(0);
+    println!("removed index 0: {}", removed);
+    println!("after remove: {:?}", fruits);
+
+    // PART 3: Accessing Items
+    let numbers = vec![10, 20, 30, 40, 50];
+
+    // Method 1
+    println!("index 0: {}", numbers[0]);
+
+    // Method 2
+    match numbers.get(2) {
+        Some(n) => println!("get(2): {}", n),
+        None => println!("index out of bounds"),
+    }
+
+    match numbers.get(99) {
+        Some(n) => println!("get(99): {}", n),
+        none => println!("get(99): index does not exists"),
+    }
+
+    println!("first: {:?}", numbers.first());
+    println!("last: {:?}", numbers.last());
+
+    // PART 4: Useful Vec Methods
+
+    let mut v = vec![3, 1, 4, 1, 5, 9, 2, 6];
+
+    println!("len: {}", v.len());
+    println!("is_empty: {}", v.is_empty());
+
+    //contains
+    println!("contains 5 : {}", v.contains(&5));
+    println!("contains 7: {}", v.contains(&7));
+
+    v.sort();
+    println!("sorted array : {:?}", v);
+
+    v.reverse();
+    println!("reversed array: {:?}", v);
+
+    // dedup => removed consecutive duplicated (sort first)
+    v.sort();
+    v.dedup();
+    println!("deduped: {:?}", v); // [1,2,3,4,5,6,9]
+
+    let mut temp = vec![1, 2, 3];
+    temp.clear();
+    println!("after clear: {:?}", temp);
+
+    // PART 5: looping over a vec
+
+    let colors = vec!["red", "green", "blue"];
+
+    for i in &colors {
+        // colors will still valid becuz we borrowed
+        println!("color : {}", i);
+    }
+
+    // loop with mut - modify each item
+    let mut prices = vec![20, 40, 60];
+    for price in &mut prices {
+        *price *= 2; // * -> dereferences -- needed to modify
+    }
+
+    println!("doubled prices: {:?}", prices);
+
+    // PART 6 : Vec of Structs  -- IMPORTANT
+
+    #[derive(Debug)]
+    struct Student {
+        name: String,
+        grade: u32,
+    }
+
+    let students = vec![
+        Student {
+            name: String::from("Alice"),
+            grade: 90,
+        },
+        Student {
+            name: String::from("in"),
+            grade: 55,
+        },
+        Student {
+            name: String::from("wonderland"),
+            grade: 87,
+        },
+    ];
+
+    for i in &students {
+        println!("{} scored {}", i.name, i.grade);
+    }
+
+    // PART 7: Slices -- a window into a Vec
+    let nums = vec![1, 2, 3, 4, 5];
+
+    // A slice is a reference to a position of a vec
+    let slice = &nums[1..4];
+    println!("slice: {:?}", slice);
+
+    let all = &nums[..];
+    println!("all: {:?}", all);
+
+    // PART 8: Useful Patterns
+
+    let numbers = vec![1, 2, 3, 4, 5];
+
+    let sum: i32 = numbers.iter().sum();
+    println!("sum: {}", sum);
+
+    println!("max: {:?}", numbers.iter().max());
+    println!("min: {:?}", numbers.iter().min());
+
+    // count items matching a condition
+    let even = numbers.iter().filter(|&x| x % 2 == 0).count();
+    println!("even count: {}", even);
+
+    // check if any item matches
+    let has_big = numbers.iter().any(|&x| x > 4);
+    println!("any > 4: {}", has_big);
+
+    // check if all items match
+    let all_positive = numbers.iter().all(|&x| x > 0);
+    println!("all positive: {}", all_positive);
+}