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  • Binary Tree Postorder Traversal

    Given a binary tree, return the postorder traversal of its nodes' values.

    For example:
    Given binary tree {1,#,2,3},

       1
        
         2
        /
       3
    

    return [3,2,1].

    C++ 实现代码:

    #include<iostream>
    #include<new>
    #include<vector>
    #include<stack>
    using namespace std;
    
    //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> postorderTraversal(TreeNode *root)
        {
            stack<TreeNode*> st;
            vector<int> ret;
            if(root==NULL)
                return vector<int>();
            st.push(root);
            TreeNode *pre=NULL;
            TreeNode *cur;
            while(!st.empty())
            {
                cur=st.top();
                if((cur->left==NULL&&cur->right==NULL)||((pre!=NULL)&&(pre==cur->left||pre==cur->right)))
                {
                    ret.push_back(cur->val);
                    st.pop();
                    pre=cur;
                }
                else
                {
                    if(cur->right)
                        st.push(cur->right);
                    if(cur->left)
                        st.push(cur->left);
                }
            }
            return ret;
        }
        void createTree(TreeNode *&root)
        {
            int i;
            cin>>i;
            if(i!=0)
            {
                root=new TreeNode(i);
                if(root==NULL)
                    return;
                createTree(root->left);
                createTree(root->right);
            }
        }
    };
    
    int main()
    {
        Solution s;
        TreeNode *root;
        s.createTree(root);
        vector<int> vec;
        vec=s.postorderTraversal(root);
        for(auto a:vec)
            cout<<a<<" ";
        cout<<endl;
    }
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  • 原文地址:https://www.cnblogs.com/wuchanming/p/4114672.html
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