题解 | 按之字形顺序打印二叉树

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param pRoot TreeNode类 
     * @return int整型vector<vector<>>
     */
    vector<vector<int>> ans;
    int depth = 0;
    void getLen(TreeNode *root, int layer) {
        if (!root) return;
        depth = max(depth, layer);
        layer ++;
        getLen(root->left, layer), getLen(root->right, layer);
    }

    void dfs(TreeNode* root, int layer) {
        if (!root) return;

        ans[layer].push_back(root->val);
        layer ++;
        dfs(root->left, layer), dfs(root->right, layer);
    }
    
    vector<vector<int> > Print(TreeNode* pRoot) {
        if (!pRoot) return {};
        // write code here
        getLen(pRoot, 1);
        cout << depth << endl;
        ans = vector<vector<int>>(depth);
        dfs(pRoot, 0);
        for (int i = 1; i < depth; i += 2) {
            reverse(ans[i].begin(), ans[i].end());
        }

        return ans;
    }
};