Leetcode68. 文本左右对齐

题目传送地址:https://leetcode.cn/problems/text-justification/

运行效率：

代码如下：

class Solution {

  public static List fullJustify(String[] words, int maxWidth) {
        List res = new ArrayList<>();
        StringBuilder row = new StringBuilder();
        for (int i = 0; i < words.length; i++) {
            String word = words[i];
            if (row.length() == 0) {  
                row.append(word);
                continue;
            }
            if (row.length() + word.length() + 1 <= maxWidth) { //因为单词与单词之间需要加一个空格，所以这里要=1
                row.append(" ").append(word);
            } else {
                res.add(row.toString());
                row = new StringBuilder();
                row.append(word);
            }
        }
        if (!"".equals(row.toString())) {
            res.add(row.toString());
        }
        List result = fillList(res, maxWidth);
        return result;
    }

    public static List fillList(List list, int maxWidth) {
        List res = new ArrayList<>();
        for (int i = 0; i < list.size(); i++) {
            String str = list.get(i);
            //如果是最后一行    文本的最后一行应为左对齐，且单词之间不插入额外的空格。
            if (i == list.size() - 1) {
                int fillBlankNum = maxWidth - str.length();
                StringBuilder stringBuilder = new StringBuilder(str);
                while (fillBlankNum > 0) {
                    stringBuilder.append(" ");
                    fillBlankNum--;
                }
                res.add(stringBuilder.toString());
                break;
            }
            int letterNum = getLetterNum(str);
            //需要填充的空格数
            int fillBlankNum = maxWidth - letterNum;
            String[] strArray = str.split(" ");
            //该行只有一个单词
            if (strArray.length == 1) {
                StringBuilder stringBuilder = new StringBuilder(strArray[0]);
                while (fillBlankNum > 0) {
                    stringBuilder.append(" ");
                    fillBlankNum--;
                }
                res.add(stringBuilder.toString());
                continue;
            }
            int avgBlankNum = fillBlankNum / (strArray.length - 1);//平均每两个单词之间应该保留的空格数
            StringBuilder blank = new StringBuilder();
            while (avgBlankNum > 0) {
                blank.append(" ");
                avgBlankNum--;
            }
            int moreBlankNum = fillBlankNum % (strArray.length - 1);//多出来的空格数
            String join = String.join(blank, strArray);
            StringBuilder stringBuilder = new StringBuilder(join);
            int fromIndex = -1;
            while (moreBlankNum > 0) {
                int index = stringBuilder.indexOf(blank.toString(), fromIndex);
                stringBuilder.insert(index, " ");
                moreBlankNum--;
                fromIndex =index+blank.length()+1;
            }
            res.add(stringBuilder.toString());
        }
        return res;
    }

    public static int getLetterNum(String str) {
        int count = 0;
        for (int i = 0; i < str.length(); i++) {
            if (str.charAt(i) != ' ') {
                count++;
            }
        }
        return count;
    }
}