first exercise!

- create exercise vec statistics calculator (shout out claude)
- finish hacky solution (it works... but at what cost)
- update current state

exercises/vec-stats/vec-stats-exercise.md

@@ -0,0 +1,26 @@
+# Exercise: Vec Statistics Calculator
+
+**Concepts practiced:** Vec operations, HashMap for counting, basic math functions
+**Objective:** Build a simple stats calculator that takes a list of numbers and returns basic statistics
+
+## Requirements:
+- Create a function `calculate_stats(numbers: Vec<i32>) -> (f64, i32, i32)` that returns (mean, median, mode)
+- Use Vec sorting for median calculation
+- Use HashMap for mode calculation (most frequent number)
+- Handle edge cases (empty vec should panic with clear message)
+
+## Success criteria:
+- Code compiles and runs
+- Test with `vec![1, 2, 3, 3, 4, 5]` returns approximately `(3.0, 3, 3)`
+
+## Stretch goal:
+Return a struct instead of tuple for better readability
+
+## Getting Started:
+1. `cd exercises`
+2. `cargo new vec-stats`
+3. `cd vec-stats`
+4. Implement the function in `src/main.rs` or `src/lib.rs`
+5. Test with the example input
+
+Expected time: 30-45 minutes