Leetcode—2415.反转二叉树的奇数层【中等】

2023每日刷题（六十）

Leetcode—2415.反转二叉树的奇数层

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BFS的C++实现代码

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* reverseOddLevels(TreeNode* root) {
        queue<TreeNode*> qu;
        vector<TreeNode*> t;
        qu.push(root);
        int level = 0;
        while(!qu.empty()) {
            int n = qu.size();
            for(int i = 0; i < n; i++) {
                TreeNode* p = qu.front();
                qu.pop();
                if(level) {
                    t.push_back(p);
                }
                if(p->left != nullptr) {
                    qu.push(p->left);
                    qu.push(p->right);
                }
            }
            level ^= 1;
            int len = t.size();
            int l = 0, r = len - 1;
            while(l < r) {
                swap((t[l])->val, (t[r])->val);
                l++;
                r--;
            }
            t.clear();
        }
        return root;
    }
};