AllTreeTraversals.cpp

//All Tree Traversals : In Pre Post order in on go using one stack 
class Solution {
public:
    vector<int>preInPostTraversal(TreeNode* root){
        stack<pair<TreeNode*,int>> st;
        st.push(root,1);
        vector<int> pre,in,post;
        if(root ==NULL)return;
        while(!st.empty())
        {
            auto it = st.top();
            st.pop();
            
            if(it.second ==1)
            {
                pre.push_back(it.first->val);
                it.second++;
                st.push(it);
                
                if(it.first->left!=NULL)
                {
                    st.push({it.first->left,1});
                    
                }
            }
            else if(it.second==2)
            {
                in.push_back(it.first->val);
                it.second++;
                st.push(it);
                if(it.first->right!=NULL)
                {
                    st.push({it.first->right,1});
                }
            }
            else
            {
                post.push_back(it.first->val);
            }
        }
    }
};