USACO 1.1 Broken Necklace

Brutal force O(N^2) solution.

#include<iostream>
#include<fstream>
#include<string>

using namespace std;

int main ()
{
  string str;
  int n, i, l, r, mx = 0;
  ifstream fin ("beads.in");
  ofstream fout ("beads.out");
  fin >> n;
  fin >> str;
  str += str;
  for (i = 0; i < n; i++) {
    l = r = 1;
    int k = i + 1;
    char flag;
    while(l < n) {
      int j = i;
      while(str[j] == 'w')
        j++;
      flag = str[j];
      if (str[k] == flag || str[k] == 'w')
        k++, l++;
      else break;
    }

    k = i + n - 2;
    while(r < n) {
      int j = i;
      while(str[j] == 'w')
        j--;
      if (str[k] == str[i + n - 1] || str[k] == 'w')
        k--, r++;
      else break;
    }

    if (l + r > mx) mx = l + r;
  }

  if (mx > n) mx = n;
  fout << mx << endl;
  return 0;
}