Add solution for Challenge 19 by kiramux (#722)

* Add solution for Challenge 19

* update ReverseSlice()

---------

Co-authored-by: go-interview-practice-bot[bot] <230190823+go-interview-practice-bot[bot]@users.noreply.github.com>

Author: kiramux

challenge-19/submissions/kiramux/solution-template.go

@@ -0,0 +1,80 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+	// Example slice for testing
+	numbers := []int{3, 1, 4, 1, 5, 9, 2, 6}
+
+	// Test FindMax
+	max := FindMax(numbers)
+	fmt.Printf("Maximum value: %d\n", max)
+
+	// Test RemoveDuplicates
+	unique := RemoveDuplicates(numbers)
+	fmt.Printf("After removing duplicates: %v\n", unique)
+
+	// Test ReverseSlice
+	reversed := ReverseSlice(numbers)
+	fmt.Printf("Reversed: %v\n", reversed)
+
+	// Test FilterEven
+	evenOnly := FilterEven(numbers)
+	fmt.Printf("Even numbers only: %v\n", evenOnly)
+}
+
+// FindMax returns the maximum value in a slice of integers.
+// If the slice is empty, it returns 0.
+func FindMax(numbers []int) int {
+	if len(numbers) == 0 {
+		return 0
+	}
+	max := math.MinInt
+	for _, v := range numbers {
+		if v > max {
+			max = v
+		}
+	}
+	return max
+}
+
+// RemoveDuplicates returns a new slice with duplicate values removed,
+// preserving the original order of elements.
+func RemoveDuplicates(numbers []int) []int {
+	seen := make(map[int]struct{}, len(numbers))
+	res := []int{}
+	for _, v := range numbers {
+		if _, ok := seen[v]; !ok {
+			seen[v] = struct{}{}
+			res = append(res, v)
+		}
+	}
+	return res
+}
+
+// ReverseSlice returns a new slice with elements in reverse order.
+func ReverseSlice(slice []int) []int {
+	if len(slice) == 0 {
+		return []int{}
+	}
+	result := make([]int, len(slice))
+	for i, v := range slice {
+		result[len(slice)-1-i] = v
+	}
+	return result
+}
+
+// FilterEven returns a new slice containing only the even numbers
+// from the original slice.
+func FilterEven(numbers []int) []int {
+	result := []int{}
+	for _, v := range numbers {
+		if v%2 == 0 {
+			result = append(result, v)
+		}
+	}
+	return result
+}