Added new practice exercises

exercises/practice/armstrong-numbers/armstrong_numbers.odin

@@ -0,0 +1,45 @@
+package armstrong_numbers
+
+to_digits :: proc(n: u128) -> [dynamic]u8 {
+	ret := make([dynamic]u8)
+	k := n
+	for k > 0 {
+		append(&ret, u8(k % 10))
+		k /= 10
+	}
+	return ret
+}
+
+fast_pow :: proc(base: u8, exp: int) -> u128 {
+	if exp == 0 {
+		return 1
+	}
+	if base < 2 {
+		return u128(base)
+	}
+	ret := u128(1)
+	a := u128(base)
+	n := exp
+	for {
+		if n % 2 == 1 {
+			ret *= a
+		}
+		n >>= 1
+		if n == 0 {
+			break
+		}
+		a *= a
+	}
+	return ret
+}
+
+is_armstrong_number :: proc(n: u128) -> bool {
+	digits := to_digits(n)
+	defer delete(digits)
+	power := len(digits)
+	sum: u128 = 0
+	for d in digits {
+		sum += fast_pow(d, power)
+	}
+	return sum == n
+}

exercises/practice/armstrong-numbers/armstrong_numbers_test.odin

@@ -0,0 +1,99 @@
+package armstrong_numbers
+import "core:testing"
+
+@(test)
+test_zero :: proc(t: ^testing.T) {
+	testing.expect(t, is_armstrong_number(0), "zero is an armstrong number")
+}
+
+@(test)
+test_single_digit :: proc(t: ^testing.T) {
+	testing.expect(t, is_armstrong_number(5), "single-digit numbers are armstrong numbers")
+}
+
+@(test)
+test_two_digit :: proc(t: ^testing.T) {
+	testing.expect(t, !is_armstrong_number(10), "there are no two-digit armstrong numbers")
+}
+
+@(test)
+test_three_digit_armstrong :: proc(t: ^testing.T) {
+	testing.expect(t, is_armstrong_number(153), "three-digit number that is an armstrong number")
+}
+
+@(test)
+test_three_digit_non_armstrong :: proc(t: ^testing.T) {
+	testing.expect(
+		t,
+		!is_armstrong_number(100),
+		"three-digit number that is not an armstrong number",
+	)
+}
+
+@(test)
+test_four_digit_armstrong :: proc(t: ^testing.T) {
+	testing.expect(t, is_armstrong_number(9_474), "four-digit number that is an armstrong number")
+}
+
+@(test)
+test_four_digit_non_armstrong :: proc(t: ^testing.T) {
+	testing.expect(
+		t,
+		!is_armstrong_number(9_475),
+		"four-digit number that is not an armstrong number",
+	)
+}
+
+@(test)
+test_seven_digit_armstrong :: proc(t: ^testing.T) {
+	testing.expect(
+		t,
+		is_armstrong_number(9_926_315),
+		"seven-digit number that is an armstrong number",
+	)
+}
+
+@(test)
+test_seven_digit_non_armstrong :: proc(t: ^testing.T) {
+	testing.expect(
+		t,
+		!is_armstrong_number(9_926_314),
+		"seven-digit number that is not an armstrong number",
+	)
+}
+
+@(test)
+test_33_digit_armstrong :: proc(t: ^testing.T) {
+	testing.expect(
+		t,
+		is_armstrong_number(186_709_961_001_538_790_100_634_132_976_990),
+		"33-digit number that is an armstrong number",
+	)
+}
+
+@(test)
+test_38_digit_non_armstrong :: proc(t: ^testing.T) {
+	testing.expect(
+		t,
+		!is_armstrong_number(99_999_999_999_999_999_999_999_999_999_999_999_999),
+		"38-digit number that is not an armstrong number",
+	)
+}
+
+@(test)
+test_largest_armstrong :: proc(t: ^testing.T) {
+	testing.expect(
+		t,
+		is_armstrong_number(115_132_219_018_763_992_565_095_597_973_971_522_401),
+		"the largest and last armstrong number",
+	)
+}
+
+@(test)
+test_largest_u128 :: proc(t: ^testing.T) {
+	testing.expect(
+		t,
+		!is_armstrong_number(340_282_366_920_938_463_463_374_607_431_768_211_455),
+		"the largest 128-bit unsigned integer value is not an armstrong number",
+	)
+}

exercises/practice/food-chain/food_chain.odin

@@ -0,0 +1,93 @@
+package food_chain
+
+import "core:strings"
+
+Animal :: struct {
+	name:      string,
+	name_long: Maybe(string),
+	phrase:    string,
+	next:      Maybe(^Animal),
+}
+
+fly := Animal {
+	name   = "fly",
+	phrase = "I don't know why she swallowed the fly. Perhaps she'll die.",
+}
+spider := Animal {
+	name      = "spider",
+	name_long = "spider that wriggled and jiggled and tickled inside her",
+	phrase    = "It wriggled and jiggled and tickled inside her.",
+	next      = &fly,
+}
+bird := Animal {
+	name   = "bird",
+	phrase = "How absurd to swallow a bird!",
+	next   = &spider,
+}
+cat := Animal {
+	name   = "cat",
+	phrase = "Imagine that, to swallow a cat!",
+	next   = &bird,
+}
+dog := Animal {
+	name   = "dog",
+	phrase = "What a hog, to swallow a dog!",
+	next   = &cat,
+}
+goat := Animal {
+	name   = "goat",
+	phrase = "Just opened her throat and swallowed a goat!",
+	next   = &dog,
+}
+cow := Animal {
+	name   = "cow",
+	phrase = "I don't know how she swallowed a cow!",
+	next   = &goat,
+}
+horse := Animal {
+	name   = "horse",
+	phrase = "She's dead, of course!",
+}
+
+verses := [8]Animal{fly, spider, bird, cat, dog, goat, cow, horse}
+
+generate_verse :: proc(builder: ^strings.Builder, i: int) {
+	animal: Maybe(^Animal) = &verses[i]
+	node, ok := animal.?
+	if !ok {
+		return
+	}
+	strings.write_string(builder, "I know an old lady who swallowed a ")
+	strings.write_string(builder, node.name)
+	strings.write_string(builder, ".\n")
+	if node.next != nil {
+		strings.write_string(builder, node.phrase)
+		strings.write_rune(builder, '\n')
+	}
+	for {
+		node := animal.? or_break
+		if node.next == nil {
+			strings.write_string(builder, node.phrase)
+			strings.write_rune(builder, '\n')
+		} else {
+			next := node.next.?
+			strings.write_string(builder, "She swallowed the ")
+			strings.write_string(builder, node.name)
+			strings.write_string(builder, " to catch the ")
+			name := next.name_long.? or_else next.name
+			strings.write_string(builder, name)
+			strings.write_string(builder, ".\n")
+		}
+		animal = node.next
+	}
+}
+
+recite :: proc(start, end: int) -> string {
+	builder := strings.builder_make()
+	defer strings.builder_destroy(&builder)
+	for i in start - 1 ..< end {
+		generate_verse(&builder, i)
+		strings.write_rune(&builder, '\n')
+	}
+	return strings.trim_right_space(strings.to_string(builder))
+}