LeetCode – Refresh – Text Justification

Clear with edge case. Such as L == 0, what to return.

class Solution {
public:
    vector<string> fullJustify(vector<string> &words, int L) {
        vector<string> result;
        if (L == 0) {
            result.push_back("");
            return result;
        }
        int len = words.size(), start = 0, wordNumber = 1, length = words[0].size(), spaceNumber = 0, extraSpace = 0;
        string line;
        for (int i = 1; i < len; i++) {
            if (length + wordNumber + words[i].size() <= L) {
                length += words[i].size();
                wordNumber++;
            } else {
                if (wordNumber == 1) {
                    spaceNumber = L - length;
                    extraSpace = 0;
                } else {
                    spaceNumber = (L - length)/(wordNumber - 1);
                    extraSpace = (L - length)%(wordNumber - 1);
                }
                for (int j = start; j < i; j++) {
                    if (j == i-1 && start != i-1) {
                        line += words[i-1];
                        break;
                    }
                    line += words[j];
                    for (int k = 0; k < spaceNumber; k++) line += ' ';
                    if (extraSpace-- > 0) line += ' ';
                }
                result.push_back(line);
                line = "";
                length = words[i].size();
                start = i;
                wordNumber = 1;
            }
        }
        for (int i = start; i < len; i++) {
            if (i == len-1) line += words[len-1];
            else line += words[i] + ' ';
        }
        for (int i = 0; i < L - length - wordNumber + 1; i++) line += ' ';
        result.push_back(line);
        return result;
    }
};