解题思路

这是一个典型的贪心算法，基本思路就是：扫描字符串数组，累加长度，当发现长度超过最大长度的时候，就把前面的几个字符串按规则组合，加入到List中。

 public List<String> fullJustify(String[] words, int maxWidth) {
        List<String> result = new ArrayList<>();
        if(words==null||words.length==0)
            return result;
        if(maxWidth==0)
        {
            result.add("");
            return result;

        }
        greedy(words,maxWidth,result);
        return result;

    }
    public void greedy(String[] words,int maxWidth,List<String> result )
    {
        if(words==null||words.length==0)
            return;
        int sum = words[0].length();
        int i;
        for (i=1;i<words.length;i++)
        {
            sum += (words[i].length()+1);
            if(sum>maxWidth)
                break;
        }
        if(sum<=maxWidth)
        {
            String re = "";

            if (words.length==1)
            {
                re += words[0];
                for (int j=0;j<maxWidth-words[0].length();j++)
                    re += " ";
                result.add(re);
                return;
            }

            int len = 0;
            for (int j=0;j<words.length-1;j++)
            {
                len += (words[j].length()+1);
                re += words[j];
                re += " ";
            }
            re += words[words.length-1];
            len += words[words.length-1].length();
            for (int j =0;j<maxWidth-len;j++)
                re += " ";
            result.add(re);
            return;
        }
        String[] s1 = Arrays.copyOfRange(words,0,i);
        String[] s2 = Arrays.copyOfRange(words,i,words.length);
        result.add(mergeString(s1,maxWidth));
        greedy(s2,maxWidth,result);
    }
    public String mergeString(String[] words,int maxWidth)
    {
        String result = "";
        int sum = 0;
        for(int i=0;i<words.length;i++)
            sum += words[i].length();
        if (words.length==1)
        {
            result += words[0];
            for (int i=0;i<maxWidth-words[0].length();i++)
                result += " ";
            return result;
        }
        int meanSpace = (maxWidth-sum)/(words.length-1);
        int moreSpace = (maxWidth-sum)%(words.length-1);
        for (int i=0;i<words.length-1;i++)
        {
            result += words[i];
            for (int j=0;j<meanSpace;j++)
                result += " ";
            if(moreSpace>0)
            {
                result += " ";
                moreSpace--;
            }
        }
        result += words[words.length-1];
        return  result;
    }