[数据结构与算法]【算法4】二叉树的层次遍历、先序、中序、后序遍历

一、二叉树的层次遍历、先序、中序、后序遍历

????????C语言这里

C++

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param root TreeNode类 
     * @return int整型vector<vector<>>
     */
    vector<vector<int> > levelOrder(TreeNode* root) {
        // write code here
        vector<vector<int>> res;//保存最后结果
        if(root==NULL) return res;
        queue<TreeNode *>q;
        q.push(root);
        while(!q.empty())
        {
            vector<int> temp;
            int n = q.size();
            for(int i=0;i<n;++i)
            {
                TreeNode *node = q.front();
                q.pop();
                temp.push_back(node->val);
                if(node->left != NULL) q.push(node->left);
                if(node->right != NULL) q.push(node->right);
                
            }
            res.push_back(temp);
        }
        return res;
    }
};

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */
vector<int> pre;
vector<int> in;
vector<int> post;
class Solution {
public:
    /**
     * 
     * @param root TreeNode类 the root of binary tree
     * @return int整型vector<vector<>>
     */
    
    void preOrder(TreeNode *root)
    {
        if(root!=NULL)
        {
            pre.push_back(root->val);
            preOrder(root->left);
            preOrder(root->right);
        }
        
    }
    void inOrder(TreeNode *root)
    {
        if(root!=NULL)
        {
            inOrder(root->left);
            in.push_back(root->val);
            inOrder(root->right);
        }
        
    }
    
    void postOrder(TreeNode *root)
    {
        if(root!=NULL)
        {
            postOrder(root->left);
            postOrder(root->right);
            post.push_back(root->val);
        }
    }
    
    
    
    vector<vector<int> > threeOrders(TreeNode* root) {
        // write code here
        vector<vector<int>> res;
        preOrder(root);
        res.push_back(pre);
        inOrder(root);
        res.push_back(in);
        postOrder(root);
        res.push_back(post);
        return res;
    }
};