leetcode 36 isValidSudoku

class Solution {public:    bool isValidSudoku(vector<vector<char>>& board) {        set<char> check;        typedef set<char>::iterator It;        typedef vector<char>::size_type sz;        sz len = board.size();        // check row        for (sz i = 0; i < len; ++i) {            for (sz j = 0; j < len; ++j) {                char ch = board[i][j];                if (ch != '.') {                    It it = check.find(ch);                    if (it != check.end())                        return false;                    else                        check.insert(ch);                }              }            check.clear();        }          // check column        for (sz i = 0; i < len; ++i) {            for (sz j = 0; j < len; ++j) {                char ch = board[j][i];                if (ch != '.') {                    It it = check.find(ch);                    if (it != check.end())                        return false;                    else                         check.insert(ch);                }            }            check.clear();        }        // check sub-boxes        for (sz i = 0; i < len; i += 3) {            for (sz j = 0; j < len; j += 3) {                for (sz m = 0; m < 3; ++m) {                    for (sz n = 0; n < 3; ++n) {                        char ch = board[i + m][j + n];                        if (ch != '.') {                            It it = check.find(ch);                            if (it != check.end())                                return false;                            else                                check.insert(ch);                        }                    }                }                check.clear();            }        }        return true;    }};

参考后

class Solution {public:    bool isValidSudoku(vector<vector<char>>& board) {        typedef vector<char>::size_type sz;        sz len = board.size();        vector<int> vc(len, 0);        vector<vector<int> > checkR(len, vc);        vector<vector<int> > checkC(checkR);        vector<vector<int> > checkB(checkR);        // check row        for (sz i = 0; i < len; ++i) {            for (sz j = 0; j < len; ++j) {                char ch = board[i][j];                if (ch != '.') {                    // check row                    if (checkR[i][ch - '0' - 1] == 1 || checkC[j][ch - '0' - 1] == 1 || checkB[i / 3 * 3 + j / 3][ch - '0' - 1] == 1)                        return false;                    else {                        // check row                        checkR[i][ch - '0' - 1] = 1;                        // check column                        checkC[j][ch - '0' - 1] = 1;                        // check sub-box                        checkB[i / 3 * 3 + j / 3][ch - '0' - 1] = 1;                    }                }              }        }        return true;    }};