m color painting

class Solution {
public:
bool isvalid(vector<vector<char>>board,char x,int r,int c){
for(int i=0;i<9;i++){
    if(board[r][i]==x){
        return false;
    }
}
for(int i=0;i<9;i++){
    if(board[i][c]==x){
        return false;
    }
}
for(int i=r/3*3;i<(r/3+1)*3;i++){
    for(int j=c/3*3;j<(c/3+1)*3;j++){
        if(board[i][j]==x){
            return false;
        }
    }
}
return true;
}



bool solveSud(vector<vector<char>>&board,int row,int col){
  
    for(int i=0;i<row;i++){
        for(int j=0;j<col;j++){
if(board[i][j]=='.'){
    for(char c='1';c<='9';c++){
        if(isvalid(board,c,i,j)==true){
            board[i][j]=c;
            if(solveSud(board,row,col)==true){
                return true;
            }
            board[i][j]='.';
           
        }
    }
    return false;
}
        }
    }
    return true;
}

    void solveSudoku(vector<vector<char>>& board) {
        int r=board.size();
        int c=board[0].size();
        cout<<r<<c<<" ";
        bool solve=solveSud(board,9,9);
        return ;
    }
};