LeetCode/cpp/even-odd-tree.cpp

#include <unordered_map>

#ifdef _MF_TEST
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) {}
};
#endif

class Solution {
    auto isEvenOddTree(std::unordered_map<int, int> &view, int level,
                       TreeNode *root) const -> bool {
        if (root == nullptr) {
            return true;
        }

        // check the parity
        if (level % 2 == root->val % 2) {
            return false;
        }

        // check the ordering
        auto &last = view[level];
        if (last != 0 && level % 2 == 0 && root->val <= last) {
            return false;
        } else if (last != 0 && level % 2 != 0 && root->val >= last) {
            return false;
        }
        last = root->val;

        if (!isEvenOddTree(view, level + 1, root->left) ||
            !isEvenOddTree(view, level + 1, root->right)) {
            return false;
        }

        return true;
    }

  public:
    bool isEvenOddTree(TreeNode *root) const {
        std::unordered_map<int, int> leftview;
        return isEvenOddTree(leftview, 0, root);
    }
};