Text Justification [LeetCode]

Problem Description:http://oj.leetcode.com/problems/text-justification/

Note: Just be careful about boundary when implementing it.

class Solution {
public:
    string genNormalLine(vector<string> &words, int L, int start, int end){
        int word_count = end - start + 1;
        string line;
        if(word_count == 1){
            line.append(words[start]);
            line.append(L-line.size(), ' ');
        }else{
            int slot_num = word_count - 1;
            int words_size = 0;
            for(int i = start; i <= end; i++)
                words_size += words[i].size();
            
            int space_num = L - words_size;
            int reminder = space_num % slot_num;
            int quotient = space_num / slot_num;
            line.append(words[start]);
            for(int i = start + 1; i <= end; i++) {
                if(reminder > 0 ){
                    line.append(quotient + 1, ' ');
                    reminder --;
                } else {
                    line.append(quotient, ' ');
                }
                
                line.append(words[i]);
            }
        }
        
        return line;
    }
    
    vector<string> fullJustify(vector<string> &words, int L) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        vector<string> formatted_lines;
        if(words.size() == 0)
            return formatted_lines;
        for(int i = 0; i < words.size();){
            int length = 0;
            
            int j = i;
            for(; j < words.size(); j ++){
                if( j == i)
                    length += words[j].size();
                else 
                    length += (1+ words[j].size());
                
                if(length > L)
                    break;
            }
            
            //put words in a line
            if(j == words.size()) {
                //last line
                string line;
                line.append(words[i]);
                for(int k = i + 1; k < words.size(); k++){
                    line.push_back(' ');
                    line.append(words[k]);
                }
                if(line.size() < L){
                    line.append(L-line.size(), ' ');
                }
                
                formatted_lines.push_back(line);
            }else {
                //normal line
                formatted_lines.push_back(genNormalLine(words,L, i, j - 1));
            }
            
            //next start index
            i = j;
        }
        
        return formatted_lines;
    }
};