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class Solution {
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 public:
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  bool isValidSudoku(vector<vector<char>> &board) {
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    int n = board.size();
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    for (int i = 0; i < n; i++) {
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      unordered_map<char, int> m;
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      for (int j = 0; j < board[i].size(); j++) {
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        if (board[i][j] == '.') {
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          continue;
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        }
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        if (m.find(board[i][j]) != m.end()) {
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          return false;
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        } else {
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          m[board[i][j]]++;
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        }
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      }
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    }
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    for (int i = 0; i < n; i++) {
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      unordered_map<char, int> m;
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      for (int j = 0; j < n; j++) {
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        if (board[j][i] == '.') {
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          continue;
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        }
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        if (m.find(board[j][i]) != m.end()) {
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          return false;
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        } else {
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          m[board[j][i]]++;
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        }
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      }
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    }
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    for (int i = 0; i < n; i += 3) {
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      for (int j = 0; j < n; j += 3) {
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        unordered_map<char, int> m;
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        for (int k = i; k <= i + 2; k++) {
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          for (int p = j; p <= j + 2; p++) {
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            if (board[k][p] == '.') {
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              continue;
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            }
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            if (m.find(board[k][p]) != m.end()) {
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              return false;
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            } else {
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              m[board[k][p]]++;
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            }
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          }
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        }
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      }
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    }
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    return true;
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  }
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};