SRM 437 D1 250

#include <algorithm>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
using namespace std;
typedef long long LL;
#define FOR(k,a,b) for(int k(a); k < (b); ++k)
#define REP(k,a) for(int k=0; k < (a); ++k)


class TheSwap {
    int mN, mIdx;
    vector<int> digits;
    vector<int> numbers;
    bool ddigit(int n)
    {
        vector<int> d(10);
        while(n)
        {
            ++d[n%10];
            if(d[n%10]==2)
                return true;
            n/=10;
        }
        return false;
    }
    bool isNeighboor(int a,int b)
    {
        if(a==b)
            return ddigit(a);
        int res=0;
        while(a)
        {
            if(a%10!=b%10)
                ++res;
            a/=10;b/=10;
        }
        return res==2;
    }
public:
    int findMax(int n, int k) {
        if(k==0)
            return n;
        mN=n;
        mIdx=0;
        int res=-1;
        vector<int>  nums;
        while(n)
        {
            digits.push_back(n%10);
            n/=10;
        }
        sort(digits.begin(),digits.end());
        do
        {
            int tmp=0;
            if (digits[0])
                REP(i,digits.size())
                {
                    tmp*=10;
                    tmp+=digits[i];
                }
            if(tmp==mN)
                mIdx=nums.size();
            nums.push_back(tmp);
        } while (next_permutation(digits.begin(),digits.end()));
        vector<vector<int> > neighboor(nums.size(),nums.size());
        REP(i,nums.size())
        REP(j,nums.size())
        {
            neighboor[i][j]=(isNeighboor(nums[i],nums[j])?1:0);
        }
        vector<vector<int> > dist(k,vector<int> (nums.size()));
        REP(i,nums.size())
            dist[0][i]=neighboor[mIdx][i];
        REP(tt,k-1)
        {
            REP(i,nums.size())
                if(dist[tt][i])
                    REP(j,nums.size())
                        if(neighboor[i][j])
                            dist[tt+1][j]=1;
        }
        REP(i,nums.size())
            if(dist[k-1][i] && nums[i]>res)
                res=nums[i];
        return res;
    }
};