Text Justification [LeetCode]

Problem Description:http://oj.leetcode.com/problems/text-justification/
Note: Just be careful about boundary when implementing it.
 1 class Solution {
 2 public:
 3     string genNormalLine(vector<string> &words, int L, int start, int end){
 4         int word_count = end - start + 1;
 5         string line;
 6         if(word_count == 1){
 7             line.append(words[start]);
 8             line.append(L-line.size(), ' ');
 9         }else{
10             int slot_num = word_count - 1;
11             int words_size = 0;
12             for(int i = start; i <= end; i++)
13                 words_size += words[i].size();
14             
15             int space_num = L - words_size;
16             int reminder = space_num % slot_num;
17             int quotient = space_num / slot_num;
18             line.append(words[start]);
19             for(int i = start + 1; i <= end; i++) {
20                 if(reminder > 0 ){
21                     line.append(quotient + 1, ' ');
22                     reminder --;
23                 } else {
24                     line.append(quotient, ' ');
25                 }
26                 
27                 line.append(words[i]);
28             }
29         }
30         
31         return line;
32     }
33     
34     vector<string> fullJustify(vector<string> &words, int L) {
35         // Note: The Solution object is instantiated only once and is reused by each test case.
36         vector<string> formatted_lines;
37         if(words.size() == 0)
38             return formatted_lines;
39         for(int i = 0; i < words.size();){
40             int length = 0;
41             
42             int j = i;
43             for(; j < words.size(); j ++){
44                 if( j == i)
45                     length += words[j].size();
46                 else 
47                     length += (1+ words[j].size());
48                 
49                 if(length > L)
50                     break;
51             }
52             
53             //put words in a line
54             if(j == words.size()) {
55                 //last line
56                 string line;
57                 line.append(words[i]);
58                 for(int k = i + 1; k < words.size(); k++){
59                     line.push_back(' ');
60                     line.append(words[k]);
61                 }
62                 if(line.size() < L){
63                     line.append(L-line.size(), ' ');
64                 }
65                 
66                 formatted_lines.push_back(line);
67             }else {
68                 //normal line
69                 formatted_lines.push_back(genNormalLine(words,L, i, j - 1));
70             }
71             
72             //next start index
73             i = j;
74         }
75         
76         return formatted_lines;
77     }
78 };