Balanced expressions challenge added.

Challenges2022.playground/Pages/Challenge#10.xcplaygroundpage/Contents.swift

@@ -0,0 +1,49 @@
+/*:
+
+ 
+ 
+
+[< Previous](@previous)           [Home](Introduction)           [Next >](@next)
+# Challenge 10: Balanced Expressions
+
+ Create a program to check that parenthesis, braces and brackets in a given expression are balanced.
+    * Balanced means that these symbols are opened and closed in order and correctly.
+    * Balanced expression: { [ a * ( c + d ) ] - 5 }
+    * Wrong balanced expression: { a * ( c + d ) ] - 5 }
+ 
+ */
+
+import Foundation
+
+func isBalanced(expression: String) -> Bool {
+    var symbolStack: [Character] = []
+    let openSym: [Character] = ["{", "[", "("]
+    let closeSym: [Character] = ["}", "]", ")"]
+    var exit = false
+    for symbol in expression {
+        if openSym.contains(symbol) {
+            symbolStack.append(symbol)
+        } else if closeSym.contains(symbol) {
+            if !symbolStack.isEmpty, symbolStack.last == openSym[closeSym.firstIndex(of: symbol)!] {
+                symbolStack.popLast()
+            } else {
+                return false
+            }
+        }
+    }
+    return symbolStack.isEmpty
+}
+
+print("Expression 1 -> \(isBalanced(expression: "{a + b [c] * (2x2)}}}}"))")
+print("Expression 2 -> \(isBalanced(expression: "{ [ a * ( c + d ) ] - 5 }"))")
+print("Expression 3 -> \(isBalanced(expression: "{ a * ( c + d ) ] - 5 }"))")
+print("Expression 4 -> \(isBalanced(expression: "{a^4 + (((ax4)}"))")
+print("Expression 5 -> \(isBalanced(expression: "{ ] a * ( c + d ) + ( 2 - 3 )[ - 5 }"))")
+print("Expression 6 -> \(isBalanced(expression: "{{{{{{(}}}}}}"))")
+print("Expression 7 -> \(isBalanced(expression: "(a"))")
+print("Expression 8 -> \(isBalanced(expression: "{ a * ( b } + 5 )"))")
+
+
+
+//: [Next](@next)
+

Challenges2022.playground/Pages/Introduction.xcplaygroundpage/Contents.swift

@@ -18,6 +18,7 @@
  * [Challenge #7: Counting words](Challenge#07)
  * [Challenge #8: From decimal to binary](Challenge#08)
  * [Challenge #9: Morse Code](Challenge#09)
+ * [Challenge #10: Balanced Expressions](Challenge#10)
  * [...]
  * [Challenge #43: Special by Halloween](Challenge#43)
  * [Challenge #44: Boomerang](Challenge#44)

Challenges2022.playground/contents.xcplayground

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<playground version='6.0' target-platform='ios' display-mode='raw' buildActiveScheme='true' importAppTypes='true'>
+<playground version='6.0' target-platform='macos' display-mode='raw' buildActiveScheme='true' importAppTypes='true'>
     <pages>
         <page name='Introduction'/>
         <page name='Challenge#00'/>
@@ -12,6 +12,7 @@
         <page name='Challenge#07'/>
         <page name='Challenge#08'/>
         <page name='Challenge#09'/>
+        <page name='Challenge#10'/>
         <page name='Challenge#43'/>
         <page name='Challenge#44'/>
         <page name='Challenge#45'/>