fullJustify

vector<string> fullJustify(vector<string> &words, int L)

{

      vector<string> result;

      if(words.empty() || L < 0)

              return result;

      int i = 0, begin = 0, end = 0;

      int length = 0;

      string formatString;

      while(i < words.size())

      {

              length = 0;

              begin  = i;

              while(i < words.size() && length + words[i].size() <= L)

              {

                      length += words[i].size();

                      //if(i > begin)

                              length += 1; // at least one space;

                      ++i;

              }

              if(begin == i)//words[i].size() >= L

              {

                      result.clear();

                      break;

              }

              end = i - 1;

              int wordCount = end - begin + 1;

              int needSpaceCount = wordCount - 1;// 3 word need 2 space

              int remaindSpace = L - length + wordCount;

              vector<int> space(needSpaceCount, 0);

              if(needSpaceCount == 0)// only one word on one line

              {

                  space.push_back(remaindSpace);

              }

              else

              {

                  for(int i = 0; i < remaindSpace; ++i)

                  {

                      ++space[i % needSpaceCount];

                  }

              }

              formatString.clear();

              int num = 0;

              for(int j = begin; j < i; ++j)

              {

                      formatString.append(words[j]);

                      if(i == words.size() && formatString.size() < L)//last line

                      {

                              formatString.push_back(' ');

                      }

                      else

                      {

                              if(j == begin)

                                  formatString.insert(formatString.end(), space[num++], ' ');

                              else if(j != i - 1)//not last && not first word;

                                  formatString.insert(formatString.end(), space[num++], ' ');

                      }

              }

              if(i == words.size() && L - formatString.size() > 0)//last line, fill ' '

              {

                      formatString.insert(formatString.end(), L - formatString.size(), ' ');

              }

              result.push_back(formatString);

      }

      return result;

}