feat: add cpp solutions to lcof problems: No. 32,33,34,35,36,39

Author: maolonglong

lcof/面试题32 - III. 从上到下打印二叉树 III/README.md

@@ -179,6 +179,36 @@ func levelOrder(root *TreeNode) [][]int {
 }
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> levelOrder(TreeNode* root) {
+        vector<vector<int>> ans;
+        if (root == NULL) return ans;
+        queue<TreeNode*> q;
+        q.push(root);
+        bool flag = false;
+        while (!q.empty()) {
+            int n = q.size();
+            vector<int> v;
+            for (int i = 0; i < n; ++i) {
+                TreeNode* node = q.front();
+                q.pop();
+                v.emplace_back(node->val);
+                if (node->left) q.push(node->left);
+                if (node->right) q.push(node->right);
+            }
+            if (flag) reverse(v.begin(), v.end());
+            flag = !flag;
+            ans.emplace_back(v);
+        }
+        return ans;
+    }
+};
+```
+
 ### **...**
 
 ```

lcof/面试题32 - III. 从上到下打印二叉树 III/Solution.cpp

@@ -0,0 +1,25 @@
+class Solution {
+public:
+    vector<vector<int>> levelOrder(TreeNode* root) {
+        vector<vector<int>> ans;
+        if (root == NULL) return ans;
+        queue<TreeNode*> q;
+        q.push(root);
+        bool flag = false;
+        while (!q.empty()) {
+            int n = q.size();
+            vector<int> v;
+            for (int i = 0; i < n; ++i) {
+                TreeNode* node = q.front();
+                q.pop();
+                v.emplace_back(node->val);
+                if (node->left) q.push(node->left);
+                if (node->right) q.push(node->right);
+            }
+            if (flag) reverse(v.begin(), v.end());
+            flag = !flag;
+            ans.emplace_back(v);
+        }
+        return ans;
+    }
+};

lcof/面试题33. 二叉搜索树的后序遍历序列/README.md

@@ -149,6 +149,35 @@ func helper(postorder []int , left,right int) bool {
 }
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    bool verifyPostorder(vector<int>& postorder) {
+        return verify(postorder, 0, postorder.size() - 1);
+    }
+
+    bool verify(vector<int>& postorder, int left, int right) {
+        if (left >= right) {
+            return true;
+        }
+        int root = postorder[right], i = left;
+        while (postorder[i] < root) {
+            ++i;
+        }
+        int mid = i;
+        while (i < right) {
+            if (postorder[i] < root) {
+                return false;
+            }
+            ++i;
+        }
+        return verify(postorder, left, mid - 1) && verify(postorder, mid, right - 1);
+    }
+};
+```
+
 ### **...**
 
 ```

lcof/面试题33. 二叉搜索树的后序遍历序列/Solution.cpp

@@ -0,0 +1,24 @@
+class Solution {
+public:
+    bool verifyPostorder(vector<int>& postorder) {
+        return verify(postorder, 0, postorder.size() - 1);
+    }
+
+    bool verify(vector<int>& postorder, int left, int right) {
+        if (left >= right) {
+            return true;
+        }
+        int root = postorder[right], i = left;
+        while (postorder[i] < root) {
+            ++i;
+        }
+        int mid = i;
+        while (i < right) {
+            if (postorder[i] < root) {
+                return false;
+            }
+            ++i;
+        }
+        return verify(postorder, left, mid - 1) && verify(postorder, mid, right - 1);
+    }
+};

lcof/面试题34. 二叉树中和为某一值的路径/README.md

@@ -176,6 +176,36 @@ func helper(node *TreeNode, target int, ans []int) {
 }
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> pathSum(TreeNode* root, int target) {
+        vector<vector<int>> ans;
+        vector<int> path;
+        dfs(root, ans, path, target);
+        return ans;
+    }
+
+    void dfs(TreeNode* root, vector<vector<int>>& ans, vector<int>& path, int target) {
+        if (root == NULL) {
+            return;
+        }
+        target -= root->val;
+        path.push_back(root->val);
+        if (root->left == NULL && root->right == NULL) {
+            if (target == 0) {
+                ans.push_back(vector<int>(path));
+            }
+        }
+        dfs(root->left, ans, path, target);
+        dfs(root->right, ans, path, target);
+        path.pop_back();
+    }
+};
+```
+
 ### **...**
 
 ```

lcof/面试题34. 二叉树中和为某一值的路径/Solution.cpp

@@ -0,0 +1,25 @@
+class Solution {
+public:
+    vector<vector<int>> pathSum(TreeNode* root, int target) {
+        vector<vector<int>> ans;
+        vector<int> path;
+        dfs(root, ans, path, target);
+        return ans;
+    }
+
+    void dfs(TreeNode* root, vector<vector<int>>& ans, vector<int>& path, int target) {
+        if (root == NULL) {
+            return;
+        }
+        target -= root->val;
+        path.push_back(root->val);
+        if (root->left == NULL && root->right == NULL) {
+            if (target == 0) {
+                ans.push_back(vector<int>(path));
+            }
+        }
+        dfs(root->left, ans, path, target);
+        dfs(root->right, ans, path, target);
+        path.pop_back();
+    }
+};

lcof/面试题35. 复杂链表的复制/README.md

@@ -209,6 +209,29 @@ func copyRandomList(head *Node) *Node {
 }
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    Node* copyRandomList(Node* head) {
+        unordered_map<Node*, Node*> m;
+        Node* p = head;
+        while (p) {
+            m[p] = new Node(p->val);
+            p = p->next;
+        }
+        p = head;
+        while (p) {
+            m[p]->next = m[p->next];
+            m[p]->random = m[p->random];
+            p = p->next;
+        }
+        return m[head];
+    }
+};
+```
+
 ### **...**
 
 ```

lcof/面试题35. 复杂链表的复制/Solution.cpp

@@ -0,0 +1,18 @@
+class Solution {
+public:
+    Node* copyRandomList(Node* head) {
+        unordered_map<Node*, Node*> m;
+        Node* p = head;
+        while (p) {
+            m[p] = new Node(p->val);
+            p = p->next;
+        }
+        p = head;
+        while (p) {
+            m[p]->next = m[p->next];
+            m[p]->random = m[p->random];
+            p = p->next;
+        }
+        return m[head];
+    }
+};

lcof/面试题36. 二叉搜索树与双向链表/README.md

@@ -149,6 +149,37 @@ var treeToDoublyList = function (root) {
 };
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    Node* treeToDoublyList(Node* root) {
+        if (root == NULL) return NULL;
+        inorder(root);
+        head->left = pre;
+        pre->right = head;
+        return head;
+    }
+
+private:
+    Node *pre, *head;
+
+    void inorder(Node* cur) {
+        if (cur) {
+            inorder(cur->left);
+            if (pre)
+                pre->right = cur;
+            else
+                head = cur;
+            cur->left = pre;
+            pre = cur;
+            inorder(cur->right);
+        }
+    }
+};
+```
+
 ### **...**
 
 ```

lcof/面试题36. 二叉搜索树与双向链表/Solution.cpp

@@ -0,0 +1,26 @@
+class Solution {
+public:
+    Node* treeToDoublyList(Node* root) {
+        if (root == NULL) return NULL;
+        inorder(root);
+        head->left = pre;
+        pre->right = head;
+        return head;
+    }
+
+private:
+    Node *pre, *head;
+
+    void inorder(Node* cur) {
+        if (cur) {
+            inorder(cur->left);
+            if (pre)
+                pre->right = cur;
+            else
+                head = cur;
+            cur->left = pre;
+            pre = cur;
+            inorder(cur->right);
+        }
+    }
+};

lcof/面试题39. 数组中出现次数超过一半的数字/README.md

@@ -81,6 +81,22 @@ var majorityElement = function (nums) {
 };
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    int majorityElement(vector<int>& nums) {
+        int votes = 0, x = 0;
+        for (int num : nums) {
+            if (votes == 0) x = num;
+            votes += x == num ? 1 : -1;
+        }
+        return x;
+    }
+};
+```
+
 ### **...**
 
 ```

lcof/面试题39. 数组中出现次数超过一半的数字/Solution.cpp

@@ -0,0 +1,11 @@
+class Solution {
+public:
+    int majorityElement(vector<int>& nums) {
+        int votes = 0, x = 0;
+        for (int num : nums) {
+            if (votes == 0) x = num;
+            votes += x == num ? 1 : -1;
+        }
+        return x;
+    }
+};