Add problem 69 and minor cleaning of other tasks

Author: tumanob

ScalaSolutions/src/main/scala/Sqrt_p69/Solution.scala

@@ -0,0 +1,38 @@
+package Sqrt_p69
+
+/**
+ * https://leetcode.com/problems/sqrtx/
+ * Given a non-negative integer x, compute and return the square root of x.
+ * Since the return type is an integer, the decimal digits are truncated, 
+ * and only the integer part of the result is returned.
+ */
+object Solution {
+  /**
+   * I am gonna Use Newton's method to calculate it as it is fun 
+   * and used in many functional programing courses as a reference
+   * 
+   * Some external reading about the method 
+   * https://blogs.sas.com/content/iml/2016/05/18/newtons-method-babylonian-square-root.html
+   */
+  val tolerance = 0.001 // when it is good enough as well a start guess
+ 
+  def mySqrt(x: Int): Int = {
+    def isGoodEnough(guess: Double): Boolean =
+      Math.abs(guess * guess - x) < tolerance
+      
+    def improve(guess: Double): Double =
+      (guess + x / guess) * 0.5
+      
+    def iterator(guess: Double): Double =
+      if (isGoodEnough(guess)) guess
+      else iterator(improve(guess))
+      
+    iterator(tolerance).toInt
+  }
+  
+  def main(args: Array[String]): Unit = {
+    println(mySqrt(3)) // 1
+    println(mySqrt(4)) // 2
+    println(mySqrt(8)) // 2
+  }
+}

ScalaSolutions/src/main/scala/TwoSum_p1/Solution.scala

@@ -11,13 +11,6 @@ package TwoSum_p1
  */
 object Solution {
 
-  def main(args: Array[String]): Unit = {
-    println(twoSum(Array(2,7,11,15), 18).mkString("[", ",", "]")) // [1,2]
-    println(twoSum(Array(2,7,11,15), 9).mkString("[", ",", "]"))  // [0,1]
-    println(twoSum(Array(2,7,11,15), 26).mkString("[", ",", "]")) // [2,3]
-  }
-
-  //leetcode submit region begin(Prohibit modification and deletion)
   def twoSum(nums: Array[Int], target: Int): Array[Int] = {
     def twoSum(index: Int, previous: Map[Int, Int]): Array[Int] = {
       previous.get(target - nums(index)) match {
@@ -27,5 +20,10 @@ object Solution {
     }
     twoSum(0, Map.empty)
   }
-  //leetcode submit region end(Prohibit modification and deletion)
+
+  def main(args: Array[String]): Unit = {
+    println(twoSum(Array(2,7,11,15), 18).mkString("[", ",", "]")) // [1,2]
+    println(twoSum(Array(2,7,11,15), 9).mkString("[", ",", "]"))  // [0,1]
+    println(twoSum(Array(2,7,11,15), 26).mkString("[", ",", "]")) // [2,3]
+  }
 }

ScalaSolutions/src/main/scala/ValidParentheses_p20/Solution.scala

@@ -14,9 +14,32 @@ import scala.collection.mutable.Stack
  */
 object Solution {
 
+  import scala.collection.mutable.Stack
+  val stack = new Stack[Char]()
+  val OpenToClose: Map[Char, Char] = Map('{' -> '}', '[' -> ']', '(' -> ')')
+
+  def checkPar(char: Char): Boolean = 
+    if (OpenToClose.contains(char)) {
+      stack.push(char)
+      true
+    } else if (stack.size > 0 && OpenToClose.get(stack.top) == Some(char)) {
+      stack.pop()
+      true
+    } else {
+      false
+    }
+  
+  def isValid(s: String): Boolean = {
+    stack.clear()
+    
+    s.size > 0 && // check edge case for empty string
+      s.forall(checkPar) && // run validation agains string elements
+      stack.size == 0 // if after check stack is not empty this is fail case
+  }
+
   def main(args: Array[String]): Unit = {
-    println(!isValid("["))
-    println(isValid("()[]{}")) // all should be true
+    println(!isValid("[")) // all should be true
+    println(isValid("()[]{}")) 
     println(isValid("()"))
     println(!isValid("(]"))
     println(isValid("[()]"))
@@ -26,24 +49,4 @@ object Solution {
     println(!isValid("{{[](A}}}}"))
     println(!isValid("{[(])}"))
   }
-
-  def isValid(s: String): Boolean = {
-    import scala.collection.mutable.Stack
-    val stack = new Stack[Char]()
-    val OpenToClose: Map[Char, Char] = Map('{' -> '}', '[' -> ']', '(' -> ')')
-
-    def checkPar(char: Char): Boolean = {
-      if (OpenToClose.contains(char)) {
-        stack.push(char)
-        true
-      } else if (stack.size > 0 && OpenToClose.get(stack.top) == Some(char)) {
-        stack.pop()
-        true
-      } else {
-        false
-      }
-    }
-
-    s.size > 0 && s.forall(checkPar) && stack.size == 0
-  }
 }