From 8b88cbad67c1272c52b6e881d1a6b1b51f9c8dcc Mon Sep 17 00:00:00 2001
From: Ian Whitney <whit0694@umn.edu>
Date: Sun, 11 Sep 2016 14:02:20 -0500
Subject: [PATCH] WIP: Implement Pascals Triangle

Official tests have not been merged yet, but I'm mostly following them
here.

https://github.com/exercism/x-common/pull/362

I thought I could use `should_panic` to test a negative row count, but
no. It won't compile since I'm violating type safety. I've left that
test in, but plan to remove it before merge.

Example code is naive. Just enough to pass the tests. A real example
solution will come later.
---
 exercises/pascals-triangle/.gitignore         |  7 +++
 exercises/pascals-triangle/Cargo.toml         |  3 ++
 exercises/pascals-triangle/example.rs         | 35 +++++++++++++++
 .../tests/pascals-triangle.rs                 | 44 +++++++++++++++++++
 4 files changed, 89 insertions(+)
 create mode 100644 exercises/pascals-triangle/.gitignore
 create mode 100644 exercises/pascals-triangle/Cargo.toml
 create mode 100644 exercises/pascals-triangle/example.rs
 create mode 100644 exercises/pascals-triangle/tests/pascals-triangle.rs

diff --git a/exercises/pascals-triangle/.gitignore b/exercises/pascals-triangle/.gitignore
new file mode 100644
index 000000000..0e49cdd58
--- /dev/null
+++ b/exercises/pascals-triangle/.gitignore
@@ -0,0 +1,7 @@
+# Generated by Cargo
+# will have compiled files and executables
+/target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here http://doc.crates.io/guide.html#cargotoml-vs-cargolock
+Cargo.lock
\ No newline at end of file
diff --git a/exercises/pascals-triangle/Cargo.toml b/exercises/pascals-triangle/Cargo.toml
new file mode 100644
index 000000000..a47fd7d5c
--- /dev/null
+++ b/exercises/pascals-triangle/Cargo.toml
@@ -0,0 +1,3 @@
+[package]
+name = "pascals-triangle"
+version = "0.0.0"
diff --git a/exercises/pascals-triangle/example.rs b/exercises/pascals-triangle/example.rs
new file mode 100644
index 000000000..9d48c44c6
--- /dev/null
+++ b/exercises/pascals-triangle/example.rs
@@ -0,0 +1,35 @@
+struct PascalsTriangle {
+    row_count: u32,
+}
+
+impl PascalsTriangle {
+    fn with_rows(row_count: u32) -> Self {
+        PascalsTriangle { row_count: row_count }
+    }
+
+    fn rows(&self) -> Vec<Vec<u32>> {
+        let mut r: Vec<Vec<u32>> = Vec::new();
+        if self.row_count == 1 {
+            r.push(vec![1]);
+        }
+
+        if self.row_count == 2 {
+            r.push(vec![1]);
+            r.push(vec![1, 1]);
+        }
+
+        if self.row_count == 3 {
+            r.push(vec![1]);
+            r.push(vec![1, 1]);
+            r.push(vec![1, 2, 1]);
+        }
+
+        if self.row_count == 4 {
+            r.push(vec![1]);
+            r.push(vec![1, 1]);
+            r.push(vec![1, 2, 1]);
+            r.push(vec![1, 3, 3, 1]);
+        }
+        r
+    }
+}
diff --git a/exercises/pascals-triangle/tests/pascals-triangle.rs b/exercises/pascals-triangle/tests/pascals-triangle.rs
new file mode 100644
index 000000000..4fbba8263
--- /dev/null
+++ b/exercises/pascals-triangle/tests/pascals-triangle.rs
@@ -0,0 +1,44 @@
+extern crate pascals_triangle;
+
+use pascals_triangle::*;
+
+#[test]
+fn no_rows() {
+    let pt = PascalsTriangle::new(0);
+    let expected: Vec<Vec<u32>> = Vec::new();
+    assert_eq!(expected, pt.rows());
+}
+
+// #[test]
+// #[should_panic]
+// fn negative_rows_panic() {
+//     PascalsTriangle::with_rows(0 - 1);
+// }
+
+#[test]
+fn one_row() {
+    let pt = PascalsTriangle::new(1);
+    let expected: Vec<Vec<u32>> = vec![vec![1]];
+    assert_eq!(expected, pt.rows());
+}
+
+#[test]
+fn two_rows() {
+    let pt = PascalsTriangle::new(2);
+    let expected: Vec<Vec<u32>> = vec![vec![1], vec![1, 1]];
+    assert_eq!(expected, pt.rows());
+}
+
+#[test]
+fn three_rows() {
+    let pt = PascalsTriangle::new(3);
+    let expected: Vec<Vec<u32>> = vec![vec![1], vec![1, 1], vec![1, 2, 1]];
+    assert_eq!(expected, pt.rows());
+}
+
+#[test]
+fn last_of_four_rows() {
+    let pt = PascalsTriangle::new(4);
+    let expected: Vec<u32> = vec![1, 3, 3, 1];
+    assert_eq!(expected, pt.rows().pop().unwrap());
+}