[Tony] WEEK 14 Solutions

binary-tree-level-order-traversal/TonyKim9401.java

@@ -0,0 +1,26 @@
+// TC: O(n)
+// need to visit all nodes
+// SC: O(n)
+// normally O(log n) required however, O(n) in the worst case
+class Solution {
+    private List<List<Integer>> output = new ArrayList<>();
+    public List<List<Integer>> levelOrder(TreeNode root) {
+        dsf(0, root);
+        return output;
+    }
+
+    private void dsf(int level, TreeNode node) {
+        if (node == null) return;
+
+        if (output.size() == level) {
+            List<Integer> inside = new ArrayList<>();
+            inside.add(node.val);
+            output.add(inside);
+        } else {
+            output.get(level).add(node.val);
+        }
+        level += 1;
+        dsf(level, node.left);
+        dsf(level, node.right);
+    }
+}

reverse-bits/TonyKim9401.java

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+public class Solution {
+    public int reverseBits(int n) {
+        // time complexity O(1)
+        // space complexity O(1)
+        int output = 0;
+
+        for (int i = 0; i < Integer.SIZE; i++) {
+            output <<= 1;
+            output += n & 1;
+            n >>= 1;
+        }
+        return output;
+    }
+}