数独检测器：帝国理工C++作业

#include <fstream>
#include <vector>
#include <iostream>
#include <string>
using namespace std;

bool check_sudoku(const vector<int>& input);
int coordtoidx(int row, int col);
void extract_row(const vector<int>& input, int row, vector<int>& output);
void extract_col(const vector<int>& input, int col, vector<int>& output);
void extract_subsquare(const vector<int>& input, int row, int col, vector<int>& output);
bool once(int num,const vector<int>& input);

int main()
{
    ifstream infile;
    cout<<"Please input a input file name"<<endl;
    string infilename;
    cin>>infilename;
    infile.open(infilename);
    if (!infile.is_open())
    {
        cout<<"could not open input file"<<endl;
        system("pause");
        exit(EXIT_FAILURE);
    }

    vector<int> input;
    int number;
    while (infile>>number)
    {
        input.push_back(number);
    }
    infile.close();

    bool isOK=check_sudoku(input);
    if (isOK)
    {
        cout<<"valid"<<endl;
    }
    else
    {
        cout<<"invalid"<<endl;
    }

    system("pause");
    return 0;
}

bool check_sudoku(const vector<int>& input)
{
    for (int i=0; i<9; i++)
    {
        vector<int> rowNumbers;
        extract_row(input,i,rowNumbers);
        for (int m=1;m<10;m++)
        {
            bool onceFlag=once(m,rowNumbers);
            if(!onceFlag)
            {
                return false;
            }
        }
    }
    for (int j=0; j<9; j++)
    {
        vector<int> colNumbers;
        extract_col(input,j,colNumbers);
        for (int m=1;m<10;m++)
        {
            bool onceFlag=once(m,colNumbers);
            if(!onceFlag)
            {
                return false;
            }
        }
    }
    for (int p=0; p<9; p=p+3)
        for (int q=0; q<9; q=q+3)
    {
        vector<int> subsquareNumbers;
        extract_subsquare(input,p,q,subsquareNumbers);
        for (int m=1;m<10;m++)
        {
            bool onceFlag=once(m,subsquareNumbers);
            if(!onceFlag)
            {
                return false;
            }
        }
    }
    return true;
}

int coordtoidx(int row, int col)
{
    return row*9+col;
}

void extract_row(const vector<int>& input, int row, vector<int>& output)
{
    for (int c=0; c<9;c++)
    {
        int idx=coordtoidx(row,c);
        output.push_back(input.at(idx));
    }
}

void extract_col(const vector<int>& input, int col, vector<int>& output)
{
    for (int r=0; r<9;r++)
    {
        int idx=coordtoidx(r,col);
        output.push_back(input.at(idx));
    }
}

void extract_subsquare(const vector<int>& input, int row, int col, vector<int>& output)
{
    for (int r=row; r<row+3;r++)
        for (int c=col; c<col+3;c++)
    {
        int idx=coordtoidx(r,c);
        output.push_back(input.at(idx));
    }
}

bool once(int num, const vector<int>& input)
{
    int count=0;
    for (unsigned int i=0; i<input.size(); i++)
    {
        if (input.at(i)==num)
        {
            count++;
        }
    }
    return count==1?true:false;
}