add scala solutions for Question 28 30 31

Author: HangMerlin

May-LeetCoding-Challenge/28-Counting-Bits/Counting-Bits.scala

@@ -0,0 +1,23 @@
+object Solution {
+  def countBits(num: Int): Array[Int] = {
+    val res = Array.fill(num + 1)(0)
+    for (i <- 0 to num) {
+      res(i) = countOne(i)
+    }
+    res
+  }
+
+  def countOne(num: Int): Int = {
+    var count = 0
+    var rest = num
+    while (rest > 1) {
+      count += rest % 2
+      rest = rest / 2
+    }
+    count + rest
+  }
+}
+
+object Solution2 {
+  def countBits(num: Int): Array[Int] = Range(0, num + 1).map(Solution.countOne).toArray
+}

May-LeetCoding-Challenge/30-K-Closest-Points-To-Origin/K-Closest-Points-To-Origin.scala

@@ -7,3 +7,44 @@ object Solution {
     (arr1(0) * arr1(0) + arr1(1) * arr1(1)) < (arr2(0) * arr2(0) + arr2(1) * arr2(1))
 
 }
+
+
+//simplest solution O(n * log(n))
+object Solution2 {
+    def kClosest(points: Array[Array[Int]], K: Int): Array[Array[Int]] =
+        points.sortBy(p => p(0) * p(0) + p(1) * p(1)).take(K)
+}
+
+//QuickSelect solution with random pivot O(n) to 0(n*n)
+object Solution3 {
+    def kClosest(points: Array[Array[Int]], K: Int): Array[Array[Int]] =
+        quickSelect(points, 0, points.length - 1, K)
+
+    def quickSelect(points: Array[Array[Int]], start: Int, end: Int, K: Int): Array[Array[Int]] = {
+        val pivot = scala.util.Random.nextInt(end - start + 1) + start
+        var i = start
+        var j = start
+        swap(points, pivot, end)
+
+        while (j < end) {
+            if (SqAddition(points(j)) <= SqAddition(points(end))) {
+                swap(points, i, j)
+                i += 1
+            }
+            j += 1
+        }
+
+        swap(points, i, j)
+        if (K == i + 1 - start) points.take(i + 1)
+        else if (K > i + 1 - start) quickSelect(points, i + 1, end, K - i - 1 + start)
+        else quickSelect(points, start, i - 1, K)
+    }
+
+    def swap(points: Array[Array[Int]], i: Int, j: Int): Unit = {
+        val tmp = points(i)
+        points(i) = points(j)
+        points(j) = tmp
+    }
+
+    def SqAddition(point: Array[Int]): Int = point(0) * point(0) + point(1) * point(1)
+}

May-LeetCoding-Challenge/31-Edit-Distance/Edit-Distance.scala

@@ -0,0 +1,14 @@
+//Dynamic programming solution
+object Solution {
+  def minDistance(word1: String, word2: String): Int = {
+    val (l1, l2) = (word1.length, word2.length)
+    val dp = Array.ofDim[Int](l1 + 1, l2 + 1)
+    for (i <- 0 to l1) { dp(i)(0) = i }
+    for (j <- 0 to l2) { dp(0)(j) = j }
+    for (i <- 0 until l1; j <- 0 until l2) {
+      if (word1(i) == word2(j)) dp(i + 1)(j + 1) = dp(i)(j)
+      else dp(i + 1)(j + 1) = (dp(i)(j) min (dp(i)(j + 1) min dp(i + 1)(j))) + 1
+    }
+    dp(l1)(l2)
+  }
+}