树的子结构java 剑指offer-优快云博客

本文链接：https://blog.youkuaiyun.com/kelexing4/article/details/105525935

本文探讨了如何判断一棵二叉树是否为另一棵二叉树的子结构，提供了详细的算法实现，包括核心函数HasSubtree和辅助函数doesTree1HaveTree2，深入解析了递归比较的过程。

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题目描述
输入两棵二叉树A，B，判断B是不是A的子结构。（ps：我们约定空树不是任意一个树的子结构）

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution{
	public static boolean HasSubtree(TreeNode tree1,TreeNode tree2){
		boolean result=false;
		if(tree1!=null && tree2!=null){
			if(tree1.val == tree2.val){
				result=doesTree1HaveTree2(tree1,tree2);
			}
            if(!result){
			result = HasSubtree(tree1.left,tree2);
		    }
		    if(!result){
			result = HasSubtree(tree1.right,tree2);
		    }
            }	
        return result;
		}
public static boolean doesTree1HaveTree2(TreeNode tree1,TreeNode tree2){
	
	if(tree2==null){
		return true;
	}
    if(tree1==null){
		return false;
	}
	if(tree1.val!=tree2.val){
		return false;
	}
	return doesTree1HaveTree2(tree1.left,tree2.left)&& doesTree1HaveTree2(tree1.right,tree2.right);
}
    
}