《编程之美:分层遍历二叉树》的另外两个实现 - Milo Yip - 博客园


给定一棵二叉树,要求按分层遍历该二叉树,即从上到下按层次访问该二叉树(每一层将单独输出一行),每一层要求访问的顺序为从左到右,并将节点依次编号。

利用了两个队列,一个储存本层的节点,另一个储存下层的节点。遍历本层的节点,把其子代节点排入下层队列。本层遍历完毕后,就可换行,并交换两个队列。
void PrintNodeByLevel(Node* root) {
    deque<Node*> Q1, Q2;
    Q1.push_back(root);
    do {
        do {
            Node* node = Q1.front();
            Q1.pop_front();
            cout << node->data << " ";
            if (node->pLeft)
                Q2.push_back(node->pLeft);
            if (node->pRight)
                Q2.push_back(node->pRight);
        } while (!Q1.empty());
        cout << endl;
        Q1.swap(Q2);
    } while(!Q1.empty());
}
是把一个结束信号放进队列里。由于使用queue<Node*>,可以插入一个空指针去表示一层的遍历结束。
void PrintNodeByLevel(Node* root) {
    queue<Node*> Q;
    Q.push(root);
    Q.push(0);
    do {
        Node* node = Q.front();
        Q.pop();
        if (node) {
            cout << node->data << " ";
            if (node->pLeft)
                Q.push(node->pLeft);
            if (node->pRight)
                Q.push(node->pRight);
        }
        else if (!Q.empty()) {
            Q.push(0);
            cout << endl;
        }
    } while (!Q.empty());
}
Read full article from 《编程之美:分层遍历二叉树》的另外两个实现 - Milo Yip - 博客园

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