Competitions » CodeFu Shortest Solution » Shortest 1 » Problem 500

Problem 500

Problem description here

This turned out to be the most difficult problem, as solving a sudoku involves permutations and a lots of checks.
This problem is shortest in C++ due to its next_permutation() implementation.

<p>class MiniSudoku
{
  public:
    string r,z,solve(string q,int p=0)
    {
      int i=0,v[999]={0};
      if (p<18)
      {
        p<1?r="IMPOSSIBLE",z="1234,1234,1234,1234":r;
        do
          solve(q,p+5);
        while (next_permutation(z.begin()+p,z.begin()+p+4));
      }
      else
      {
        for (; i<19; z[i]!=q[i]&&q[i]<99?p=0:1, i++)
          for (int b[]={i/5,i%5,(i/5>1)+2*(i%5>1)}, k=0;p&&++k<4;)
            p = z[i]<45?p:v[99*k+9*b[k-1]+z[i]]++ < 1;
        p&&z<r?r=z:r;
      }
      return r;
  }
};</p>

Highlights

string r,z,solve(string q,int p=0) definition of string and method at the same time
solve(string q,int p=0) default parameter, to be used when calling the method recursively
int b[]={i/5,i%5,(i/5>1)+2*(i%5>1)} definition and initialization of an array

Competitions
- CodeFu 2023
  - Final Round