LC#338 optimal, returns array containting bit counts, O(N) time, O(N) Space

Author: NirmalSilwal

Leetcode/easy/CountingBits338.java

@@ -26,15 +26,30 @@ private static int countBinaryOnes(int num) {
 return count;
 }
 
+// optimal code using DP
+public static int[] countBitsDP(int n) {
+int[] ans = new int[n + 1];
+ans[0] = 0;
+
+for (int index = 1; index <= n; index++) {
+if (index % 2 == 0) { // even
+ans[index] = ans[index / 2];
+} else { // odd
+ans[index] = 1 + ans[index / 2];
+}
+}
+return ans;
+}
+
 public static void main(String[] args) {
 System.out.println(Arrays.toString(countBits(2)));
 System.out.println(Arrays.toString(countBits(5)));
 System.out.println(Arrays.toString(countBits(0)));
+
+System.out.println("\noptimal\n");
+
+System.out.println(Arrays.toString(countBitsDP(2)));
+System.out.println(Arrays.toString(countBitsDP(5)));
+System.out.println(Arrays.toString(countBitsDP(0)));
 }
 }
-
-/* output:
-[0, 1, 1]
-[0, 1, 1, 2, 1, 2]
-[0]
-*/