Binary Tree traversal in C++

binary-tree-traversal.cpp

// Pre-order traversal
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    vector<int> poResult;
public:
    vector<int> preorderTraversal(TreeNode* root) {
        if(root)   poResult.push_back(root->val);
        if(root)   preorderTraversal(root->left);
        if(root)   preorderTraversal(root->right);
        return poResult;
    }
};

// In-order traversal
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    vector<int> ioResult;
public:
    vector<int> inorderTraversal(TreeNode* root) {
        if(root)    inorderTraversal(root->left);
        if(root)    ioResult.push_back(root->val);
        if(root)    inorderTraversal(root->right);
        return ioResult;
    }
};

// Post-order traversal
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    vector<int> poResult;
public:
    vector<int> postorderTraversal(TreeNode* root) {
        if(root)    postorderTraversal(root->left);
        if(root)    postorderTraversal(root->right);
        if(root)    poResult.push_back(root->val);
        return poResult;
    }
};