feat(src): add 102-levelOrder, 102-levelOrder, 104-maxDepth

Author: kwu130

src/102-levelOrder.cpp

@@ -0,0 +1,63 @@
+//
+// Created by 1412 on 2025/12/1.
+//
+
+#include <bits/stdc++.h>
+#include "common.h"
+
+using namespace std;
+using treeHelper::TreeNode;
+
+class Solution {
+public:
+    vector<vector<int>> levelOrder(TreeNode* root) {
+        vector<vector<int>> res;
+        if (root == nullptr) return res;
+        queue<TreeNode*> q;
+        q.push(root);
+        while (!q.empty()) {
+            size_t n = q.size();
+            vector<int> level;
+            while (n--) {
+                TreeNode* node = q.front();
+                q.pop();
+                level.push_back(node->val);
+                if (node->left != nullptr) q.push(node->left);
+                if (node->right != nullptr) q.push(node->right);
+            }
+            res.push_back(level);
+        }
+        return res;
+    }
+};
+
+void test() {
+    Solution s;
+    int nullptr_value = -1;
+    TreeNode* root = treeHelper::build({3, 9, 20, nullptr_value, nullptr_value, 15, 7}, nullptr_value);
+    vector<vector<int>> expected = {
+        {3},
+        {9, 20},
+        {15, 7}
+    };
+    vector<vector<int>> res = s.levelOrder(root);
+    assert(res == expected);
+    treeHelper::free(root);
+
+    root = treeHelper::build({1}, nullptr_value);
+    expected = {{1}};
+    res = s.levelOrder(root);
+    assert(res == expected);
+    treeHelper::free(root);
+
+    root = treeHelper::build({}, nullptr_value);
+    expected = {};
+    res = s.levelOrder(root);
+    assert(res == expected);
+    treeHelper::free(root);
+}
+
+int main() {
+    test();
+    return 0;
+}

src/103-zigzagLevelOrder.cpp

@@ -0,0 +1,68 @@
+//
+// Created by 1412 on 2025/12/1.
+//
+
+#include <bits/stdc++.h>
+#include "common.h"
+
+using namespace std;
+using treeHelper::TreeNode;
+
+class Solution {
+public:
+    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
+        vector<vector<int>> res;
+        if (root == nullptr) return res;
+        queue<TreeNode*> q;
+        q.push(root);
+        bool left_to_right = true;
+        while (!q.empty()) {
+            size_t n = q.size();
+            vector<int> level;
+            while (n--) {
+                TreeNode* node = q.front();
+                q.pop();
+                level.push_back(node->val);
+                if (node->left != nullptr) q.push(node->left);
+                if (node->right != nullptr) q.push(node->right);
+            }
+            if (!left_to_right) {
+                ranges::reverse(level);
+            }
+            left_to_right = !left_to_right;
+            res.push_back(level);
+        }
+        return res;
+    }
+};
+
+void test() {
+    Solution s;
+    int nullptr_value = -1;
+    TreeNode* root = treeHelper::build({3, 9, 20, nullptr_value, nullptr_value, 15, 7}, nullptr_value);
+    vector<vector<int>> res = s.zigzagLevelOrder(root);
+    vector<vector<int>> expected = {
+        {3},
+        {20, 9},
+        {15, 7}
+    };
+    assert(res == expected);
+    treeHelper::free(root);
+
+    root = treeHelper::build({1}, nullptr_value);
+    expected = {{1}};
+    res = s.zigzagLevelOrder(root);
+    assert(res == expected);
+    treeHelper::free(root);
+
+    root = treeHelper::build({}, nullptr_value);
+    expected = {};
+    res = s.zigzagLevelOrder(root);
+    assert(res == expected);
+    treeHelper::free(root);
+}
+
+int main() {
+    test();
+    return 0;
+}

src/104-maxDepth.cpp

@@ -0,0 +1,38 @@
+//
+// Created by 1412 on 2025/12/1.
+//
+
+#include <bits/stdc++.h>
+#include "common.h"
+
+using namespace std;
+using treeHelper::TreeNode;
+
+class Solution {
+public:
+    int maxDepth(TreeNode* root) {
+        if (root == nullptr) return 0;
+        return max(maxDepth(root->left), maxDepth(root->right)) + 1;
+    }
+};
+
+void test() {
+    Solution s;
+    int nullptr_value = -1;
+    TreeNode* root = treeHelper::build({3, 9, 20, nullptr_value, nullptr_value, 15, 7}, nullptr_value);
+    assert(s.maxDepth(root) == 3);
+    treeHelper::free(root);
+
+    root = treeHelper::build({1, nullptr_value}, nullptr_value);
+    assert(s.maxDepth(root) == 1);
+    treeHelper::free(root);
+
+    root = treeHelper::build({}, nullptr_value);
+    assert(s.maxDepth(root) == 0);
+    treeHelper::free(root);
+}
+
+int main() {
+    test();
+    return 0;
+}