[juhui-jeong] Solution Week14

Author: juhui-jeong

binary-tree-level-order-traversal/juhui-jeong.java

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+// BFS 구현
+// null 처리 잘 확인할 것...
+class Solution {
+    public List<List<Integer>> levelOrder(TreeNode root) {
+        List<List<Integer>> result = new ArrayList<>();
+        if (root == null) return result;
+
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.offer(root);
+
+        while(!queue.isEmpty()) {
+            int size = queue.size();
+            List<Integer> level = new ArrayList<>();
+
+            for (int i = 0; i < size; i++) {
+                TreeNode cur = queue.poll();
+                level.add(cur.val);
+
+                if (cur.left != null) queue.offer(cur.left);
+                if (cur.right != null) queue.offer(cur.right);
+            }
+            result.add(level);
+        }
+        return result;
+    }
+}

counting-bits/juhui-jeong.java

@@ -0,0 +1,24 @@
+
+
+class Solution {
+    public int[] countBits(int n) {
+        ArrayList<Integer> list = new ArrayList<>();
+
+        for (int i = 0; i <= n; i++) {
+            int result = i;
+            int cnt = 0;
+
+            while(result > 0) {
+                cnt += result%2;
+                result /= 2;
+            }
+
+            list.add(cnt);
+        }
+        int[] ans = new int[list.size()];
+        for (int i = 0; i < list.size(); i++) {
+            ans[i] = list.get(i);
+        }
+        return ans;
+    }
+}