树的子结构 java

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树的子结构 java

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）

代码1：

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

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

    }

}
*/
public class Solution {
    public boolean HasSubtree(TreeNode root1,TreeNode root2) {
        boolean flag = false;
        if(root1 != null && root2 != null){
            if(root1.val == root2.val){
                flag = getCompare(root1, root2);
            }
            if(!flag){
                flag = HasSubtree(root1.left, root2);
            }
            if(!flag){
                flag = HasSubtree(root1.right, root2);
            }
        }
        return flag;
    }
    
    public boolean getCompare(TreeNode root1,TreeNode root2){
        if(root2 == null){
            return true;
        }
        if(root1 == null){
            return false;
        }
        if(root1.val != root2.val){
            return false;
        }
        return getCompare(root1.left, root2.left) && getCompare(root1.right, root2.right);
    }
}

代码2：

public class Solution {
    public boolean HasSubtree(TreeNode root1,TreeNode root2) {
        boolean flag = false;
        if(root1 != null && root2 != null){
            if(root1.val == root2.val){
                flag = getCompare(root1, root2);
            }
            if(!flag){
                flag = HasSubtree(root1.left, root2);
            }
            if(!flag){
                flag = HasSubtree(root1.right, root2);
            }
        }
        return flag;
    }
    private boolean getCompare(TreeNode root1,TreeNode root2){
        boolean flag = false;
        if(root2 == null){
            flag = true;
        }
        if(root1 != null && root2 != null && root1.val == root2.val){
            flag = getCompare(root1.left, root2.left) && getCompare(root1.right, root2.right);
        }
        return flag;
    }
}