606 a tree problem, not so hard

606-20231208-pass/main.cpp

@@ -0,0 +1,94 @@
+#include<stdcpp.h>
+using namespace std;
+struct TreeNode {
+    int val;
+    TreeNode *left;
+    TreeNode *right;
+    TreeNode() : val(0), left(nullptr), right(nullptr) {}
+    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+};
+void create(int * val, int cnt, TreeNode *cur,int idx){
+    int left_idx = (idx + 1) * 2 - 1;
+    int right_idx = (idx + 1) * 2 ;
+    if(left_idx >= cnt && right_idx >= cnt) {
+        cur->left = nullptr;
+        cur->right = nullptr;
+        return;
+    }
+    if(val[left_idx] == -1 || left_idx >= cnt){
+        cur -> left = nullptr;
+    }else{
+        TreeNode * left_child = new TreeNode(val[left_idx]);
+        cur->left = left_child;
+        create(val,cnt,left_child,left_idx);
+    }
+    if(val[right_idx] == -1 || right_idx >= cnt){
+        cur -> right = nullptr;
+    }else{
+        TreeNode * right_child = new TreeNode(val[right_idx]);
+        cur->right = right_child;
+        create(val, cnt, right_child, right_idx);
+    }
+    return;
+}
+void traverse(TreeNode* node){
+    cout<<node->val<<' ';
+    if(node->left != nullptr){
+        traverse(node->left);
+    }
+    if(node->right != nullptr){
+        traverse(node->right);
+    }
+    return;
+}
+TreeNode* createTree(int * val, int cnt){
+    TreeNode * root = new TreeNode(val[0]);
+    cout<<"create a tree"<<endl;
+    create(val,cnt,root, 0);
+    traverse(root);
+    cout<<"\ndone"<<endl;
+    return root;
+}
+
+class Solution{
+    public:
+    string traverse(TreeNode * node, string &str){
+        str.push_back((char)('0'+node->val));
+        if(node -> left == nullptr && node -> right == nullptr) return str;
+        if(node -> left == nullptr){
+            str.push_back('(');
+            str.push_back(')');
+        }else{
+            str.push_back('(');
+            traverse(node->left, str);
+            str.push_back(')');
+        }
+        if(node -> right == nullptr){
+            return str;
+        }else{
+            str.push_back('(');
+            traverse(node->right, str);
+            str.push_back(')');
+            return str;
+        }
+        
+    }
+    string tree2str(TreeNode * root){
+        string rlt = "";
+        return traverse(root,rlt);
+    }
+
+};
+
+int main(){
+    Solution sol;
+    int ex1_val[4] = {1,2,3,4};
+    TreeNode * ex1 = createTree(ex1_val,4);
+    cout<<sol.tree2str(ex1)<<endl;
+    int ex2_val[5] = {1,2,3,-1,4};
+    TreeNode * ex2 = createTree(ex2_val, 5);
+    cout<<sol.tree2str(ex2)<<endl;
+
+    return 0;
+}