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  • Subtree of Another Tree

    Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node's descendants. The tree s could also be considered as a subtree of itself.

    Example 1:
    Given tree s:

         3
        / 
       4   5
      / 
     1   2
    

    Given tree t:

       4 
      / 
     1   2
    

    Return true, because t has the same structure and node values with a subtree of s.

    Example 2:
    Given tree s:

         3
        / 
       4   5
      / 
     1   2
        /
       0
    

    Given tree t:

       4
      / 
     1   2
    

    Return false.

    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     *     int val;
     *     TreeNode left;
     *     TreeNode right;
     *     TreeNode(int x) { val = x; }
     * }
     */
    class Solution {
        
        public boolean isSubtree(TreeNode s, TreeNode t) {
            if(s==null&&t==null) return true;
            if(s==null&&t!=null) return false;
            if(s!=null&&t==null) return false;
            return isSameTree(s,t)||isSubtree(s.left,t)||isSubtree(s.right,t);   
        }
        
        public boolean isSameTree(TreeNode a, TreeNode b){
            if(a==null&&b==null) return true;
            if(a==null&&b!=null) return false;
            if(a!=null&&b==null) return false;
            if(a.val!=b.val) return false;
            return isSameTree(a.left,b.left)&&isSameTree(a.right,b.right);
        }
            
    }
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  • 原文地址:https://www.cnblogs.com/hygeia/p/9789051.html
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