2024/8/31 LeetCode Hot100 binaryTree

src/main/java/com/cool/hot100/binary_tree/Num199.java

@@ -0,0 +1,64 @@
+package com.cool.hot100.binary_tree;
+
+import sun.reflect.generics.tree.Tree;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
+/**
+ * Created with IntelliJ IDEA.
+ *
+ * @Author: Cool
+ * @Date: 2024/09/01/1:58
+ * DayNumber 2
+ * Hard 2
+ * Level 4
+ */
+public class Num199 {
+
+
+    public List<Integer> rightSideView(TreeNode root) {
+//        List<Integer> list = new ArrayList<>();
+//        dfs(root, list, 0);
+//        return list;
+        return bfs(root);
+    }
+
+    private List<Integer> bfs(TreeNode root) {
+        List<Integer> list = new ArrayList<>();
+        if (root == null) return list;
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.add(root);
+        while (!queue.isEmpty()) {
+            int size = queue.size();
+            for (int i = 0; i < size; i++) {
+                TreeNode node = queue.poll();
+                if (node != null && node.left != null) {
+                    queue.add(node.left);
+                }
+                if (node != null && node.right != null) {
+                    queue.add(node.right);
+                }
+                if (i == size - 1 && node != null) {
+                    list.add(node.val);
+                }
+            }
+        }
+        return list;
+    }
+
+
+    //此为dfs解法
+    private void dfs(TreeNode root, List<Integer> list, int deep) {
+        if (root == null) return;
+        if (list.size() == deep) {
+            list.add(root.val);
+        }
+        dfs(root.right, list, ++deep);
+        dfs(root.left, list, deep);
+    }
+
+
+}

src/main/java/com/cool/hot100/binary_tree/Num230.java

@@ -0,0 +1,35 @@
+package com.cool.hot100.binary_tree;
+
+/**
+ * Created with IntelliJ IDEA.
+ *
+ * @Author: Cool
+ * @Date: 2024/09/01/1:43
+ * DayNumber 1
+ * Hard 2
+ * Level 3
+ */
+public class Num230 {
+
+
+    public int kthSmallest(TreeNode root, int k) {
+        int[] arr = new int[k];
+        dfs(root, arr, 0);
+        return arr[arr.length - 1];
+    }
+
+    private int dfs(TreeNode root, int[] arr, int num) {
+        if (root == null) {
+            return num;
+        }
+        if (num >= arr.length) return num;
+        num = dfs(root.left, arr, num);
+        if (num >= arr.length) return num;
+        arr[num++] = root.val;
+        if (num >= arr.length) return num;
+        num = dfs(root.right, arr, num);
+
+        return num;
+    }
+
+}