[LeetCode]: 100: Same Tree

最新推荐文章于 2025-09-07 20:32:33 发布

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最新推荐文章于 2025-09-07 20:32:33 发布

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CC 4.0 BY-SA版权

文章标签：数据结构与算法 c/c++

原文链接：http://www.cnblogs.com/savageclc26/p/4779894.html

本文介绍了一种通过先序、中序遍历来判断两棵二叉树是否相同的算法，并提供了一种更简洁高效的实现方式，仅需递归比较节点值及左右子树。

题目：

Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

解析：

比较两个二叉树是否相同采用将二叉树进行“先序遍历”，“中序遍历”和“后序遍历”，如果其中有两种遍历的结果相同，则这两个二叉树相等

代码：

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    
    public boolean isSameTree(TreeNode p, TreeNode q) {
        
        String ResultL1 = Front(p);
        String ResultL2 = Front(q);
        
        String ResultL3 = Middle(p);
        String ResultL4 = Middle(q);
        /*
        String ResultL5 = Last(p);
        String ResultL6 = Last(q);
        */
        
        if(ResultL1.equals(ResultL2) && ResultL3.equals(ResultL4)){
             return true;
        }
        else{
            return false;
        }
    }
    
    public static String Front(TreeNode Tree){
        if(Tree == null){
            return "X";
        }
        
        String strResult  = "";
        
        strResult += Tree.val;
        strResult += Front(Tree.left);
        strResult += Front(Tree.right);

        return strResult;
    }
    
    public static String Middle(TreeNode Tree){
        if(Tree == null){
            return "X";
        }
        
        String strResult  = "";
        strResult += Middle(Tree.left);
        strResult += Tree.val;
        strResult += Middle(Tree.right);

        return strResult;
    }
    
    public static String Last(TreeNode Tree){
        if(Tree == null){
            return "X";
        }
        
        String strResult  = "";
        strResult += Last(Tree.left);
        strResult += Last(Tree.right);
        strResult += Tree.val;

        return strResult;
    }
    
}

网上高人的代码如下：添加了空树的判断

    bool isSameTree(TreeNode *p, TreeNode *q) {  
        // Start typing your C/C++ solution below  
        // DO NOT write int main() function  
        if (p == NULL && q == NULL)  
            return true;  
        else if (p == NULL || q == NULL)  
            return false;  
        return p->val == q->val && isSameTree(p->left, q->left)  
            && isSameTree(p->right, q->right);  
    }