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What is the O(n) of this leetcode solution?


I was wondering what the O(n) for this leetcode solution would be. To clarify, this code is supposed to validate a sudoku puzzle. The portion of my code that would run the longest would be the last block. Since there are 4 for loops in this code block, would it take O(n^4) time? What about space complexity?

class Solution {
    public boolean isValidSudoku(char[][] board) {
        HashMap<Character, Integer> sudoku = new HashMap<Character, Integer>();
        final int size = 9;
        
        for(int i = 0; i < size; i++) {
            for(int j = 0; j < size; j++) {
                char num = board[i][j];
                
                if(num != '.') {
                    if(!sudoku.containsKey(num)) {
                        sudoku.put(num, 1);
                    }
                    else {
                        return false;
                    }
                }
            }
            sudoku.clear();
        }
        
        for(int i = 0; i < size; i++) {
            for(int j = 0; j < size; j++) {
                char num = board[j][i];
                
                if(num != '.') {
                    if(!sudoku.containsKey(num)) {
                        sudoku.put(num, 1);
                    }
                    else {
                        return false;
                    }
                }
            }
            sudoku.clear();
        }
        
         for(int i = 0; i <= 6; i+=3) {
            for(int j = 0; j <= 6; j+=3) {
                for(int r = 0; r < 3; r++) {
                    for(int c = 0; c < 3; c++) {
                         char num = board[r+i][c+j];
                
                        if(num != '.') {
                            if(!sudoku.containsKey(num)) {
                                sudoku.put(num, 1);
                            }
                            else {
                                return false;
                            }
                        }
                    }
                }
                sudoku.clear();
            }
        }
   
        return true;
    }
}



Source: https://stackoverflow.com/questions/70553761/what-is-the-on-of-this-leetcode-solution

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