LeetCode（剑指 Offer）- 26. 树的子结构

Posted 2022-04-23 放羊的牧码

题目链接：点击打开链接

题目大意：略

解题思路：略

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AC 代码

• Java

/**
 * Definition for a binary tree node.
 * public class TreeNode 
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x)  val = x; 
 * 
 */

// 解决方案(1)
class Solution 

    private boolean ok = false;

    public boolean isSubStructure(TreeNode A, TreeNode B) 
        if (null == B) 
            return false;
        

        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(A);
        TreeNode b = B;
        while (!queue.isEmpty()) 
            TreeNode a = queue.poll();
            if (a.val == b.val) 
                bfs(a, b);
                if (ok) 
                    break;
                 else 
                    b = B;
                
            
            if (a.left != null) 
                queue.offer(a.left);
            
            if (a.right != null) 
                queue.offer(a.right);
            
        

        return ok;
    

    private void bfs(TreeNode sa, TreeNode sb) 
        Queue<TreeNode> qa = new LinkedList<>();
        Queue<TreeNode> qb = new LinkedList<>();
        qa.offer(sa);
        qb.offer(sb);
        while (!qb.isEmpty()) 
            TreeNode a = qa.poll();
            TreeNode b = qb.poll();
            if (a == null || a.val != b.val) 
                return;
            
            if (a.left != null) 
                qa.offer(a.left);
            
            if (a.right != null) 
                qa.offer(a.right);
            
            if (b.left != null) 
                qb.offer(b.left);
            
            if (b.right != null) 
                qb.offer(b.right);
            
        
        ok = true;
    


// 解决方案(2)
class Solution 
    public boolean isSubStructure(TreeNode A, TreeNode B) 
        return (A != null && B != null) && (recur(A, B) || isSubStructure(A.left, B) || isSubStructure(A.right, B));
    
    boolean recur(TreeNode A, TreeNode B) 
        if(B == null) return true;
        if(A == null || A.val != B.val) return false;
        return recur(A.left, B.left) && recur(A.right, B.right);
    

• C++

class Solution 
public:
    bool isSubStructure(TreeNode* A, TreeNode* B) 
        return (A != nullptr && B != nullptr) && (recur(A, B) || isSubStructure(A->left, B) || isSubStructure(A->right, B));
    
private:
    bool recur(TreeNode* A, TreeNode* B) 
        if(B == nullptr) return true;
        if(A == nullptr || A->val != B->val) return false;
        return recur(A->left, B->left) && recur(A->right, B->right);
    
;

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