Add solution for Challenge 19 (#716)

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

Author: iamsurajmandal

challenge-19/submissions/iamsurajmandal/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) < 1) {
+        return 0
+    }
+	max := int(math.Inf(-1))
+    for i := 0; i < len(numbers); i++ {
+        if (numbers[i] > max) {
+            max = numbers[i]
+        }
+    }	
+	return max
+}
+
+// RemoveDuplicates returns a new slice with duplicate values removed,
+// preserving the original order of elements.
+func RemoveDuplicates(numbers []int) []int {
+	// TODO: Implement this function
+	hs := map[int]bool{}
+	result := []int{}
+	for _, value := range numbers {
+	    _, exists := hs[value]
+	    if !exists {
+	      hs[value] = true
+	      result = append(result, value)
+	    }
+	}
+	return result
+}
+
+// ReverseSlice returns a new slice with elements in reverse order.
+func ReverseSlice(slice []int) []int {
+    result := []int{}
+	// TODO: Implement this function
+	for i := len(slice) - 1; i >= 0 ; i-- {
+	    result = append(result, slice[i])
+	}
+	return result
+}
+
+// FilterEven returns a new slice containing only the even numbers
+// from the original slice.
+func FilterEven(numbers []int) []int {
+	result := []int{}
+	for _, value := range numbers{
+	    if (value % 2 == 0 ) {
+	        result = append(result, value)
+	    }
+	}
+	return result
+}