子树

描述

控制台

245. 子树

有两个不同大小的二叉树： T1 有上百万的节点； T2 有好几百的节点。请设计一种算法，判定 T2 是否为 T1的子树。

样例

下面的例子中 T2 是 T1 的子树：

       1                3
      / \              / 
T1 = 2   3      T2 =  4
        /
       4

下面的例子中 T2 不是 T1 的子树：

       1               3
      / \               \
T1 = 2   3       T2 =    4
        /
       4

注意事项

若 T1 中存在从节点 n 开始的子树与 T2 相同，我们称 T2 是 T1 的子树。也就是说，如果在 T1 节点 n 处将树砍断，砍断的部分将与 T2 完全相同。

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */

class Solution {
public:
    /**
     * @param T1: The roots of binary tree T1.
     * @param T2: The roots of binary tree T2.
     * @return: True if T2 is a subtree of T1, or false.
     */
    bool isSubtree(TreeNode * T1, TreeNode * T2) {
        // write your code here
        if(T1==NULL && T2==NULL) return true;
        if(T1==NULL && T2!=NULL) return false;
        if(T1!=NULL && T2==NULL) return true;
        string res1=Seriers(T1);
        string res2=Seriers(T2);
        int R=res2.size();
        int pos=0;
        for(int i=0;i<res1.size();)
        {
            if(res1[i]!=res2[pos])
            {
                int k=res2.size()-1;
                while(k>0 && R<res2.size() && res2[k]!=res1[R])
                {
                    k--;
                }
                i=R-k;
                pos=0;
                R=i+res2.size();
            }else
            {
                if(pos==res2.size()-1)
                {
                    return true;
                }
                pos++;
                i++;
            }
        }
        return false;
    }
private:
    string Seriers(TreeNode* TREE)
    {
        if(TREE==NULL) return "#!";
        string res=to_string(TREE->val)+'!';
        res+=Seriers(TREE->left);
        res+=Seriers(TREE->right);
        return res;
         
    } 
};

######################################################
/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */

public class Solution {
    /**
     * @param T1: The roots of binary tree T1.
     * @param T2: The roots of binary tree T2.
     * @return: True if T2 is a subtree of T1, or false.
     */
    public boolean isSubtree(TreeNode T1, TreeNode T2) {
        // write your code here
        if(T1==null && T2==null) return true;
        if(T1!=null && T2==null) return true;
        if(T1==null && T2!=null) return false;
        char[] str=Seriers(T1).toCharArray();
        char[] match=Seriers(T2).toCharArray();
        int pos=0;
        int R=match.length;
        for (int i=0;i<str.length ; )
        {
            if(str[i]!=match[pos])
            {
                int k=match.length -1;
                while(k>0 && R<str.length && str[R]!=match[k])
                {
                    k--;
                }
                i=R-k;
                pos=0;
                R=i+match.length;
            }else
            {
                if(pos==match.length-1)
                {
                    return true;
                }
                pos++;
                i++;
            }
        }
        return false;
        
    }
    
    private String Seriers(TreeNode tree)
    {
        if(tree==null) return "#!";
        String res=String.valueOf(tree.val)+'!';
        res+=Seriers(tree.left);
        res+=Seriers(tree.right);
        return res;
    }
}

###############################################################

"""
Definition of TreeNode:
class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left, self.right = None, None
"""

class Solution:
    """
    @param T1: The roots of binary tree T1.
    @param T2: The roots of binary tree T2.
    @return: True if T2 is a subtree of T1, or false.
    """
    def isSubtree(self, T1, T2):
        # write your code here
        if T1 == None and T2 == None:
            return True
        if T1 == None and T2 != None:
            return False
        if T1 != None and T2 == None:
            return True
        strr = []
        match = []
        self.Seriers(T1, strr)
        self.Seriers(T2, match)
        pos=0
        index=0
        R=len(match)
        while index<len(strr):
            if strr[index]!=match[pos]:
                k=len(match)-1
                while k>0 and R<len(match) and match[k]!=strr[R]:
                    k-=1
                index=R-k
                pos=0
                R=index+len(match)
            else:
                if pos==len(match)-1:
                    return True
                index+=1
                pos+=1
        return False
        
    
    def Seriers(self,Tree,strings):
        if Tree==None:
            return strings.append('#!')
        strings.append(str(Tree.val)+'!')
        self.Seriers(Tree.left,strings)
        self.Seriers(Tree.right,strings)