Added Selection Sort along with 9 test cases (#31)

Author: therexdy

CONTRIBUTING.md

@@ -43,6 +43,7 @@ Every project is managed by the `build.zig` file.
 ├── sort
 │   ├── bubbleSort.zig
 │   ├── insertionSort.zig
+│   ├── selectionSort.zig
 │   ├── mergeSort.zig
 │   ├── quickSort.zig
 │   └── radixSort.zig

build.zig

@@ -42,6 +42,13 @@ pub fn build(b: *std.Build) void {
             .name = "insertionSort.zig",
             .category = "sort",
         });
+    if (std.mem.eql(u8, op, "sort/selectionSort"))
+        buildAlgorithm(b, .{
+            .optimize = optimize,
+            .target = target,
+            .name = "selectionSort.zig",
+            .category = "sort",
+        });
 
     // Search algorithms
     if (std.mem.eql(u8, op, "search/bSearchTree"))

runall.zig

@@ -33,6 +33,7 @@ pub fn main() !void {
     try runTest(allocator, "sort/radixsort");
     try runTest(allocator, "sort/mergesort");
     try runTest(allocator, "sort/insertsort");
+    try runTest(allocator, "sort/selectionSort");
 
     // Search
     try runTest(allocator, "search/bSearchTree");

sort/selectionSort.zig

@@ -0,0 +1,93 @@
+const std = @import("std");
+const mem = std.mem;
+const expect = std.testing.expect;
+
+// Reference: https://www.geeksforgeeks.org/dsa/selection-sort-algorithm-2/
+fn sort(A: []i64) void {
+    for (0..A.len) |i| {
+        var smallest: usize = i;
+
+        for (i + 1..A.len) |j| {
+            // condetion: < for ascending order and > for descending order
+            if (A[j] < A[smallest]) {
+                smallest = j;
+            }
+        }
+
+        mem.swap(i64, &A[i], &A[smallest]);
+    }
+}
+
+test "empty array" {
+    var A = [_]i64{};
+    sort(&A);
+    for (A, 0..) |value, i| {
+        try expect(value == i);
+    }
+}
+
+test "single element" {
+    var A = [_]i64{0};
+    sort(&A);
+    for (A, 0..) |value, i| {
+        try expect(value == i);
+    }
+}
+
+test "reverse order" {
+    var A = [_]i64{ 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 };
+    sort(&A);
+    for (A, 0..) |value, i| {
+        try expect(value == i);
+    }
+}
+
+test "all same" {
+    var A = [_]i64{ 0, 0, 0, 0, 0, 0 };
+    const forTest = [_]i64{ 0, 0, 0, 0, 0, 0 };
+    sort(&A);
+    for (A, forTest) |i, j| {
+        try expect(i == j);
+    }
+}
+
+test "sorted" {
+    var A = [_]i64{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+    sort(&A);
+    for (A, 0..) |value, i| {
+        try expect(value == i);
+    }
+}
+
+test "partially sorted" {
+    var A = [_]i64{ 0, 1, 2, 3, 4, 9, 6, 5, 8, 7 };
+    sort(&A);
+    for (A, 0..) |value, i| {
+        try expect(value == i);
+    }
+}
+
+test "last two unordered" {
+    var A = [_]i64{ 0, 1, 2, 3, 4, 5, 6, 7, 9, 8 };
+    sort(&A);
+    for (A, 0..) |value, i| {
+        try expect(value == i);
+    }
+}
+
+test "first two unordered" {
+    var A = [_]i64{ 1, 0, 2, 3, 4, 5, 6, 7, 8, 9 };
+    sort(&A);
+    for (A, 0..) |value, i| {
+        try expect(value == i);
+    }
+}
+
+test "negative numbers with duplicates" {
+    var A = [_]i64{ -6, -3, 6, 0, -7, 2, 1, 8, -5, 1, 6 };
+    const sortedA = [_]i64{ -7, -6, -5, -3, 0, 1, 1, 2, 6, 6, 8 };
+    sort(&A);
+    for (A, sortedA) |i, j| {
+        try expect(i == j);
+    }
+}