1424. Diagonal Traverse II

O(C) time O(log(max(m, n))) space
当一个binary tree来level order traverse

class Solution {
public:
    vector<int> findDiagonalOrder(vector<vector<int>>& nums) {
        queue<pair<int, int>> q{{{0, 0}}};
        vector<int> res;
        while (!q.empty()) {
            auto [r, c] = q.front(); q.pop();
            res.push_back(nums[r][c]);
            if (r + 1 < nums.size() && c == 0) { // 因为每一行都非空，所以只有第一个需要添加左子，剩下的统一添加右子即可去重
                q.emplace(r + 1, c);
            }
            if (c + 1 < nums[r].size()) {
                q.emplace(r, c + 1);
            }
        }
        return res;
    }
};