missing number solution added

2023_09_18/.vscode/launch.json

@@ -0,0 +1,7 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": []
+}

2023_09_18/learders_in_an_array/src/main.rs

@@ -1,6 +1,5 @@
 // Given an array A of positive integers. Your task is to find the leaders in the array. An element of array is leader if it is greater than or equal to all the elements to its right side. The rightmost element is always a leader.
 
-// Declare a function that takes a slice of i32 as input and returns a Vec<i32>
 fn leaders_in_an_array(arr: &[i32]) -> Vec<i32> {
     // Empty vector to store the leaders
     let mut leaders = Vec::new();
@@ -13,6 +12,7 @@ fn leaders_in_an_array(arr: &[i32]) -> Vec<i32> {
         if arr[i] > max {
             // Set the max value to the current element
             max = arr[i];
+            // Add the max value to the leaders vector
             leaders.push(max);
         }
     }

2023_09_18/missing_number/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "missing_number"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

2023_09_18/missing_number/README.md

@@ -0,0 +1,24 @@
+# Comments on the solution
+
+We are using a simple mathematical approach that it's pretty much self-explanatory. We can express the sum of all numbers from `0` to `n` as `n * (n + 1) / 2`. We can then subtract the sum of the array from the sum of all numbers from `0` to `n` to get the missing number.
+
+### Complexity
+
+- **Time Complexity:** `O(n)` - We are iterating over the array once.
+- **Space Complexity:** `O(1)` - We are not using any extra space.
+
+---
+
+### Solution in Rust
+
+```rust
+fn missing_number(nums: Vec<i32>) -> i32 {
+    (1..=nums.len() as i32).sum::<i32>() - nums.iter().sum::<i32>()
+}
+```
+
+where we use the `..=` range operator to create a range from `1` to the length of the input vector, and then sum the values in that range using the `sum` method
+
+### Leetcode result
+
+![](https://i.imgur.com/qW2tNVm.png)

2023_09_18/missing_number/src/main.rs

@@ -0,0 +1,10 @@
+// Given an array nums containing n distinct numbers in the range [0, n], return the only number in the range that is missing from the array.
+
+fn missing_number(nums: Vec<i32>) -> i32 {
+    (1..=nums.len() as i32).sum::<i32>() - nums.iter().sum::<i32>()
+}
+
+fn main() {
+    let nums = vec![3, 0, 1];
+    println!("{}", missing_number(nums));
+}