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程式語言 - LeetCode - C++ - 226. Invert Binary Tree

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題目：


解答一：

/**
 * 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* invertTree(TreeNode* root) {
        queue<TreeNode*> st;

        if (!root) {
            return root;
        }

        st.push(root);
        while (!st.empty()) {
            TreeNode *t = st.front(); st.pop();

            swap(t->left, t->right);

            if (t->right) {
                st.push(t->right);
            }
            if (t->left) {
                st.push(t->left);
            }
        }

        return root;
    }
};

解法二：

/**
 * 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* invertTree(TreeNode* root) {
        if (!root) {
            return root;
        }

        swap(root->left, root->right);
        invertTree(root->left);
        invertTree(root->right);

        return root;
    }
};