solve

Author: sonjh1217

counting-bits/sonjh1217.swift

@@ -0,0 +1,35 @@
+class Solution {
+    // Brute Force
+    // O(nlogn) time / O(n) space
+    func countBits(_ n: Int) -> [Int] {
+        var numberOfOnes = [Int]()
+        for i in 0...n {
+            var numberOfOne = 0
+            var i = i
+            
+            while i > 0 {
+                numberOfOne += i & 1
+                i >>= 1
+            }
+            
+            numberOfOnes.append(numberOfOne)
+        }
+        
+        return numberOfOnes
+    }
+    
+    // Dynamic Programming
+    // O(n) time / O(n) space
+    func countBitsDP(_ n: Int) -> [Int] {
+        var numberOfOnes = [Int](repeating: 0, count: n + 1)
+        if n < 1 {
+            return numberOfOnes
+        }
+        
+        for i in 1...n {
+            numberOfOnes[i] = numberOfOnes[i >> 1] + (i & 1)
+        }
+        return numberOfOnes
+        
+    }
+}