[se6816] WEEK 14 Solutions

binary-tree-level-order-traversal/se6816.java

@@ -0,0 +1,27 @@
+class Solution {
+    public List<List<Integer>> levelOrder(TreeNode root) {
+        if(root == null) {
+            return new ArrayList<>();
+        }
+        List<List<Integer>> list = new ArrayList<>();
+        dfs(root, 0, list);
+        return list;
+    }
+
+    public void dfs(TreeNode node, int depth, List<List<Integer>> list) {
+        if(list.size() == depth) {
+            list.add(new ArrayList<>());
+        }
+
+        List<Integer> dest = list.get(depth);
+        dest.add(node.val);
+
+        if(node.left != null) {
+            dfs(node.left, depth + 1, list);
+        }
+
+        if(node.right != null) {
+            dfs(node.right, depth + 1, list);
+        }
+    }
+}

counting-bits/se6816.java

@@ -0,0 +1,9 @@
+class Solution {
+    public int[] countBits(int n) {
+        int[] list = new int[n + 1];
+        for(int i = 0; i <= n; i++) {
+            list[i] = Integer.bitCount(i);
+        }
+        return list;
+    }
+}

house-robber-ii/se6816.java

@@ -0,0 +1,30 @@
+class Solution {
+    public int rob(int[] nums) {
+        if(nums.length == 1) {
+            return nums[0];
+        }
+
+        // 첫 집을 턴 경우
+        int[] dp = new int[nums.length];
+        dp[0] = nums[0];
+        if(nums.length != 1) {
+            dp[1] = Math.max(nums[0], nums[1]);
+        }
+
+        for (int i = 2; i < nums.length; i++) {
+            dp[i] = Math.max(dp[i-1], nums[i] + dp[i-2]);
+        }
+
+        // 첫 집 안 턴 경우 
+        int[] dp2 = new int[nums.length-1];
+        dp2[0] = nums[1];      
+        if (nums.length > 2) {
+            dp2[1] = Math.max(nums[1], nums[2]);
+        }
+        for (int i = 2; i < nums.length-1; i++) {
+            dp2[i] = Math.max(dp2[i-1], nums[i+1] + dp2[i-2]);  
+        }
+
+        return Math.max(dp[nums.length-2], dp2[nums.length-2]);
+    }
+}