UVA 10001 Garden of Eden

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题目太难懂了，看了老半天搞不清楚。。。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
int n, m, d[8], g[100], f[100], ff;
string s;

void work(int x)
{
  if (ff) return;
  if (x == m)
  {
    f[m] = f[0]; f[m + 1] = f[1];
    int y = f[m - 2] * 4 + f[m - 1] * 2 + f[m];
    int z = f[m - 1] * 4 + f[m] * 2 + f[m + 1];
    if (d[y] == g[m - 1] && d[z] == g[0]) ff = 1;
    return;
  }
  for (int i = 0; i <= 1; i++)
  {
    f[x] = i;
    if (x < 2) work(x + 1);
    else
    {
      int y = f[x] + f[x - 1] * 2 + f[x - 2] * 4;
      if (d[y] == g[x - 1]) work(x + 1);
    }
    if (ff) return;
  }
}

int main()
{
  while (cin >> n >> m >> s)
  {
    for (int i = 0; i < 8; i++, n /= 2) d[i] = n % 2;
    for (int i = 0; i < m; i++) g[i] = s[i] - '0';
    ff = 0;   work(0);
    if (ff) cout << "REACHABLE" << endl;
    else cout << "GARDEN OF EDEN" << endl;
  }
  return 0;
}