2023-11-22 15:49:02 +0000 UTC

class Solution {
public:
    vector<int> findDiagonalOrder(vector<vector<int>>& nums) {
        unordered_map<int, vector<int>> groups;
        for (int row = nums.size() - 1; row >= 0; row--) {
            for (int col = 0; col < nums[row].size(); col++) {
                int diagonal = row + col;
                groups[diagonal].push_back(nums[row][col]);
            }
        }
        
        vector<int> ans;
        int curr = 0;
        
        while (groups.find(curr) != groups.end()) {
            for (int num : groups[curr]) {
                ans.push_back(num);
            }
            
            curr++;
        }
        
        return ans;
    }
};