Add matrix (#502)

Author: keiravillekode

config.json

@@ -846,6 +846,14 @@
         ],
         "difficulty": 4
       },
+      {
+        "slug": "matrix",
+        "name": "Matrix",
+        "uuid": "fc517d08-fb7f-49ed-a474-ce78d3c5ac7d",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
+      },
       {
         "slug": "nth-prime",
         "name": "Nth Prime",

exercises/practice/matrix/.docs/instructions.md

@@ -0,0 +1,38 @@
+# Instructions
+
+Given a string representing a matrix of numbers, return the rows and columns of that matrix.
+
+So given a string with embedded newlines like:
+
+```text
+9 8 7
+5 3 2
+6 6 7
+```
+
+representing this matrix:
+
+```text
+    1  2  3
+  |---------
+1 | 9  8  7
+2 | 5  3  2
+3 | 6  6  7
+```
+
+your code should be able to spit out:
+
+- A list of the rows, reading each row left-to-right while moving top-to-bottom across the rows,
+- A list of the columns, reading each column top-to-bottom while moving from left-to-right.
+
+The rows for our example matrix:
+
+- 9, 8, 7
+- 5, 3, 2
+- 6, 6, 7
+
+And its columns:
+
+- 9, 5, 6
+- 8, 3, 6
+- 7, 2, 7

exercises/practice/matrix/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "matrix.zig"
+    ],
+    "test": [
+      "test_matrix.zig"
+    ],
+    "example": [
+      ".meta/example.zig"
+    ]
+  },
+  "blurb": "Given a string representing a matrix of numbers, return the rows and columns of that matrix.",
+  "source": "Exercise by the JumpstartLab team for students at The Turing School of Software and Design.",
+  "source_url": "https://turing.edu"
+}

exercises/practice/matrix/.meta/example.zig

@@ -0,0 +1,51 @@
+const std = @import("std");
+const mem = std.mem;
+
+/// Returns the selected row of the matrix.
+pub fn row(allocator: mem.Allocator, s: []const u8, index: i32) ![]i16 {
+    return select(allocator, s, index, 0);
+}
+
+/// Returns the selected column of the matrix.
+pub fn column(allocator: mem.Allocator, s: []const u8, index: i32) ![]i16 {
+    return select(allocator, s, 0, index);
+}
+
+pub fn select(allocator: mem.Allocator, s: []const u8, required_row: i32, required_column: i32) ![]i16 {
+    var list = std.array_list.Managed(i16).init(allocator);
+    errdefer list.deinit();
+    var current_row: i32 = 1;
+    var current_column: i32 = 1;
+    var number: i16 = 0;
+    var negate: bool = false;
+
+    for (0.., s) |i, c| {
+        switch (c) {
+            '0'...'9' => {
+                number = 10 * number + (c - '0');
+                if (i + 1 == s.len or s[i + 1] < '0') {
+                    if (negate) {
+                        number = -number;
+                        negate = false;
+                    }
+                    if (current_row == required_row or current_column == required_column) {
+                        try list.append(number);
+                    }
+                    number = 0;
+                }
+            },
+            ' ' => {
+                current_column += 1;
+            },
+            '\n' => {
+                current_row += 1;
+                current_column = 1;
+            },
+            '-' => {
+                negate = true;
+            },
+            else => unreachable,
+        }
+    }
+    return list.toOwnedSlice();
+}

exercises/practice/matrix/.meta/tests.toml

@@ -0,0 +1,34 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[ca733dab-9d85-4065-9ef6-a880a951dafd]
+description = "extract row from one number matrix"
+
+[5c93ec93-80e1-4268-9fc2-63bc7d23385c]
+description = "can extract row"
+
+[2f1aad89-ad0f-4bd2-9919-99a8bff0305a]
+description = "extract row where numbers have different widths"
+
+[68f7f6ba-57e2-4e87-82d0-ad09889b5204]
+description = "can extract row from non-square matrix with no corresponding column"
+
+[e8c74391-c93b-4aed-8bfe-f3c9beb89ebb]
+description = "extract column from one number matrix"
+
+[7136bdbd-b3dc-48c4-a10c-8230976d3727]
+description = "can extract column"
+
+[ad64f8d7-bba6-4182-8adf-0c14de3d0eca]
+description = "can extract column from non-square matrix with no corresponding row"
+
+[9eddfa5c-8474-440e-ae0a-f018c2a0dd89]
+description = "extract column where numbers have different widths"

exercises/practice/matrix/matrix.zig

@@ -0,0 +1,18 @@
+const std = @import("std");
+const mem = std.mem;
+
+/// Returns the selected row of the matrix.
+pub fn row(allocator: mem.Allocator, s: []const u8, index: i32) ![]i16 {
+    _ = allocator;
+    _ = s;
+    _ = index;
+    @compileError("please implement the row function");
+}
+
+/// Returns the selected column of the matrix.
+pub fn column(allocator: mem.Allocator, s: []const u8, index: i32) ![]i16 {
+    _ = allocator;
+    _ = s;
+    _ = index;
+    @compileError("please implement the column function");
+}

exercises/practice/matrix/test_matrix.zig

@@ -0,0 +1,86 @@
+const std = @import("std");
+const testing = std.testing;
+
+const matrix = @import("matrix.zig");
+const row = matrix.row;
+const column = matrix.column;
+
+test "extract row from one number matrix" {
+    const expected = &[_]i16{1};
+    const s = "1";
+    const actual = try row(testing.allocator, s, 1);
+    defer testing.allocator.free(actual);
+    try testing.expectEqualSlices(i16, expected, actual);
+}
+
+test "can extract row" {
+    const expected = &[_]i16{ 3, 4 };
+    const s = "1 2\n3 4";
+    const actual = try row(testing.allocator, s, 2);
+    defer testing.allocator.free(actual);
+    try testing.expectEqualSlices(i16, expected, actual);
+}
+
+test "extract row where numbers have different widths" {
+    const expected = &[_]i16{ 10, 20 };
+    const s = "1 2\n10 20";
+    const actual = try row(testing.allocator, s, 2);
+    defer testing.allocator.free(actual);
+    try testing.expectEqualSlices(i16, expected, actual);
+}
+
+test "can extract row from non-square matrix with no corresponding column" {
+    const expected = &[_]i16{ 8, 7, 6 };
+    const s = "1 2 3\n4 5 6\n7 8 9\n8 7 6";
+    const actual = try row(testing.allocator, s, 4);
+    defer testing.allocator.free(actual);
+    try testing.expectEqualSlices(i16, expected, actual);
+}
+
+test "extract column from one number matrix" {
+    const expected = &[_]i16{1};
+    const s = "1";
+    const actual = try column(testing.allocator, s, 1);
+    defer testing.allocator.free(actual);
+    try testing.expectEqualSlices(i16, expected, actual);
+}
+
+test "can extract column" {
+    const expected = &[_]i16{ 3, 6, 9 };
+    const s = "1 2 3\n4 5 6\n7 8 9";
+    const actual = try column(testing.allocator, s, 3);
+    defer testing.allocator.free(actual);
+    try testing.expectEqualSlices(i16, expected, actual);
+}
+
+test "can extract column from non-square matrix with no corresponding row" {
+    const expected = &[_]i16{ 4, 8, 6 };
+    const s = "1 2 3 4\n5 6 7 8\n9 8 7 6";
+    const actual = try column(testing.allocator, s, 4);
+    defer testing.allocator.free(actual);
+    try testing.expectEqualSlices(i16, expected, actual);
+}
+
+test "extract column where numbers have different widths" {
+    const expected = &[_]i16{ 1903, 3, 4 };
+    const s = "89 1903 3\n18 3 1\n9 4 800";
+    const actual = try column(testing.allocator, s, 2);
+    defer testing.allocator.free(actual);
+    try testing.expectEqualSlices(i16, expected, actual);
+}
+
+test "row with negative numbers" {
+    const expected = &[_]i16{ -57, 9, -42 };
+    const s = "1 2 4\n-57 9 -42\n10 0 65";
+    const actual = try row(testing.allocator, s, 2);
+    defer testing.allocator.free(actual);
+    try testing.expectEqualSlices(i16, expected, actual);
+}
+
+test "column with negative numbers" {
+    const expected = &[_]i16{ -4, -42, -465 };
+    const s = "1 2 -4\n-57 9 -42\n10 0 -465";
+    const actual = try column(testing.allocator, s, 3);
+    defer testing.allocator.free(actual);
+    try testing.expectEqualSlices(i16, expected, actual);
+}