chore(Go): add selection sort (#820)

algorithms/Go/README.md

@@ -19,7 +19,8 @@
 ## Sorting
 - [Bubble Sort](sorting/bubble-sort.go)
 - [Insertion Sort](sorting/insertion-sort.go)
-- [Quicksort](sorting/quicksort.go)
+- [Quick Sort](sorting/quicksort.go)
+- [Selection Sort](sorting/selection-sort.go)
 
 ## Recursion
 - [Fibonacci](recursion/fibonacci.go)

algorithms/Go/sorting/selection-sort.go

@@ -0,0 +1,62 @@
+/*
+	Selection sort algorithm sorts an array by repeatedly finding the minimum element (considering ascending order) from unsorted part and putting it at the beginning.
+	The algorithm maintains two subarrays in a given array:
+		The subarray which is already sorted.
+		Remaining subarray which is unsorted.
+	Average Time Complexity: O(n^2)
+
+	Link for reference: https://www.geeksforgeeks.org/selection-sort/
+
+*/
+
+package sorting
+
+import "fmt"
+
+func RunSelectionSortRec() {
+	arr := []int{7, 4, 7, 3, 2}
+	selSortRec(arr, len(arr)-1) //using recursion
+	fmt.Println(arr)            // 2, 3, 4, 7, 7
+}
+func RunSelectionSortIter() {
+	arr := []int{7, 4, 7, 3, 1}
+	selSort(arr)     //using iteration
+	fmt.Println(arr) // 1, 3, 4, 7, 7
+}
+
+//sort using iterative method
+func selSort(arr []int) {
+	for arrIndex := range arr {
+		minVal := arr[arrIndex]
+		minIndex := arrIndex
+		for subIndex := arrIndex + 1; subIndex < len(arr); subIndex++ {
+			if arr[subIndex] < minVal {
+				minVal = arr[subIndex]
+				minIndex = subIndex
+			}
+		}
+		arr[minIndex], arr[arrIndex] = arr[arrIndex], arr[minIndex]
+	}
+}
+
+//sort using recursive method
+func selSortRec(arr []int, i int) {
+	if i < 0 {
+		return
+	}
+	maxIn := maxSel(arr, i)
+	//i = len(arr)-1
+	if i != maxIn {
+		arr[i], arr[maxIn] = arr[maxIn], arr[i]
+	}
+	selSortRec(arr, i-1)
+}
+func maxSel(arr []int, i int) int {
+	if i > 0 {
+		maxIn := maxSel(arr, i-1)
+		if arr[i] < arr[maxIn] {
+			return maxIn
+		}
+	}
+	return i
+}