added swift and some algorithm

Program's_Contributed_By_Contributors/Swift_Programs/Prim Algorithm/Prim Algorithm.playground/Contents.swift

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+import Foundation
+
+
+
+func prims (_ matrix : [[Int]]) {
+    var selected = 0
+    var selectedSoFar = Set<Int>()
+    selectedSoFar.insert( (matrix[selected].enumerated().min{ $0.element < $1.element }?.offset)! )
+
+    while selectedSoFar.count < matrix.count {
+        var minValue = Int.max
+        var minIndex = selected
+        var initialRow = 0
+        for row in selectedSoFar {
+            let candidateMin = matrix[row].enumerated().filter{$0.element > 0 && !selectedSoFar.contains($0.offset) }.min{ $0.element < $1.element }
+            if (minValue > candidateMin?.element ?? Int.max ) {
+                minValue = candidateMin?.element ?? Int.max
+                minIndex = (candidateMin?.offset) ?? 0
+                initialRow = row
+            }
+        }
+        print ("edge value \(minValue) with \(initialRow) to \(minIndex)")
+        selectedSoFar.insert(minIndex)
+        selected = (minValue)
+    }
+}
+
+let input = [[0,9,75,0,0],[9,0,95,19,42],[75,95,0,51,66],[0,19,51,0,31],[0,42,66,31,0]]
+prims(input)
+

Program's_Contributed_By_Contributors/Swift_Programs/Prim Algorithm/Prim Algorithm.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

Program's_Contributed_By_Contributors/Swift_Programs/Prim Algorithm/README.markdown

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+# Prim's Algorithm
+
+Prim's Algorithm is an algorithm that finds a minimum spanning tree for a weighted undirected graph. This means it finds a subset of the edges that forms a tree that includes every vertex, where the total weight of all the edges in the tree is minimized.
+
+
+## How does it work
+
+We start from one vertex and keep adding edges with the lowest weight until we reach our goal. 
+1. Initialize the minimum spanning tree with a vertex chosen at random
+2. Find all the edges that connect the tree to new verticles, find the minimum and add it to the tree
+3. Keep repeating step 2 until we get a minimum spanning tree
+
+## Time complexity
+Adjacency matrix, searching : O(|V|^{2})
+binary heap and adjacency list : O((|V|+|E|)\log |V|)= O(|E|\log |V|)
+Fibonacci heap and adjacency list : O(|E|+|V|\log |V|)
+
+##Sources 
+
+[1]: 
+https://www.programiz.com/dsa/prim-algorithm
+[2]:
+https://www.raywenderlich.com/books/data-structures-algorithms-in-swift/v4.0/chapters/45-prim-s-algorithm-challenges
+[3]: https://codereview.stackexchange.com/questions/215897/swift-prims-algorithm

Program's_Contributed_By_Contributors/Swift_Programs/Selection Sort/README .markdown

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+# Selection Sort
+
+The 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.
+1) The subarray which is already sorted. 
+2) Remaining subarray which is unsorted.
+In every iteration of selection sort, the minimum element (considering ascending order) from the unsorted subarray is picked and moved to the sorted subarray. 
+
+## How does it work
+
+arr[] = 64 25 12 22 11
+
+// Find the minimum element in arr[0...4]
+// and place it at beginning
+11 25 12 22 64
+
+// Find the minimum element in arr[1...4]
+// and place it at beginning of arr[1...4]
+11 12 25 22 64
+
+// Find the minimum element in arr[2...4]
+// and place it at beginning of arr[2...4]
+11 12 22 25 64
+
+// Find the minimum element in arr[3...4]
+// and place it at beginning of arr[3...4]
+11 12 22 25 64 
+
+## Time complexity
+Best/Worst/Average Case: = 0(n^2)
+
+##Sources 
+
+[1]: 
+Example and details:
+https://www.geeksforgeeks.org/selection-sort/

Program's_Contributed_By_Contributors/Swift_Programs/Selection Sort/SelectionSort.playground/Contents.swift

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+import UIKit
+
+public func selectionSort<T: Comparable>(_ array: [T], _ isOrderedBefore: (T, T) -> Bool) -> [T] {
+    var a = array
+    guard array.count > 1 else { return array }
+
+    for x in 0 ..< a.count - 1 {
+
+        // print out the lowest value of the array
+        var lowest = x
+        for y in x + 1 ..< a.count {
+            if isOrderedBefore(a[y], a[lowest]) {
+                lowest = y
+            }
+        }
+
+        // swap lowest value with index
+        if x != lowest {
+            a.swapAt(x, lowest)
+        }
+    }
+    return a
+}
+let list = [ 2, -1, 11, 6, 5, 1, 0, 22, 1, 4, 8, 43 ]
+selectionSort(list, <)
+selectionSort(list, >)

Program's_Contributed_By_Contributors/Swift_Programs/Selection Sort/SelectionSort.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>