LeetCode（剑指 Offer）- 26. 树的子结构

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

// 解决方案(1)
class Solution {

    private boolean ok = false;

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

        Queue 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 qa = new LinkedList<>();
        Queue 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);
    }
};