leetcode2:inorder tranversal

inorder tranversal

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> inorderTraversal(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> *p_vec = new vector<int>();
        
       inorderRecur( root, *p_vec);
        
        return *p_vec;
        
    }
    
    void  inorderRecur( TreeNode *root, vector<int> & vec) {
        if( root == NULL ) return;
        inorderRecur(root->left, vec);
        vec.push_back( root->val );
        inorderRecur(root->right, vec);
        
    }
};

iterative approach:

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
#include <stack> 
 
using namespace std; 
 
class Solution {
public:
    vector<int> inorderTraversal(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> *p_vec = new vector<int>();
        stack<TreeNode*> tree_stack;
        
        while(1) {
            if( root) {
                tree_stack.push( root);
                root = root->left;
            } else {
                if( tree_stack.empty() ) break;
                
                TreeNode * tmp = tree_stack.top();
                
                p_vec->push_back( tmp->val );
                tree_stack.pop();
                root = tmp->right;
                
                
            }
            

            
        }
        
        
        return *p_vec;
        
    }
    

};

preorder traversal:

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> inorderTraversal(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> * vec = new vector<int>();
        stack<TreeNode*> my_stack;
        
        while(1) {
            if( root) {
                vec->push_back(root->val);
                my_stack.push(root);
                root = root->left;
            } else {
                if(my_stack.empty() ){
                    break;
                }
                
                TreeNode* tmp = my_stack.top();
                my_stack.pop();
                root = tmp->right;
            }
            
            
        }
        
        return *vec;
    }
};
post order traversal:

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> inorderTraversal(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> * vec = new vector<int>();
        stack<TreeNode*> my_stack;
        
        while(1) {
            if( root) {
                my_stack.push(root);
                root = root->left;
            } else {
                if(my_stack.empty() ){
                    break;
                }
                TreeNode* tmp = my_stack.top();
                if(tmp->right != NULL) {
                    root = tmp->right;    
                } else {
                    vec->push_back( tmp->val);
                    my_stack.pop();
                    root = my_stack.top();
                }
                
            }
            
            
        }
        
        return *vec;
    }
};