Text Justification.java

// Runtime: 4 ms (Top 15.97%) | Memory: 42.1 MB (Top 76.75%)
class Solution {
    public List<String> fullJustify(String[] words, int maxWidth) {
        List<String> unBalanced = new ArrayList<>();
        List<String> balanced = new ArrayList<>();
        int numSpaces = 0;

        StringBuffer sb = new StringBuffer();
        //Following code creates a list of unbalanced lines by appending words and 1 space between them
        for(String word : words){

            if(sb.length() == 0){
                sb.append(word);
            }else{
                if(sb.length() + 1 + word.length() <= maxWidth){
                    sb.append(" "+word);
                }else{
                    unBalanced.add(sb.toString());
                    sb = new StringBuffer(word);
                }
            }

        }

        if(sb.length() >0){
            unBalanced.add(sb.toString());
        }

        for(int j = 0; j < unBalanced.size(); j++){
            String line = unBalanced.get(j);
            numSpaces = maxWidth - line.length();
            StringBuffer lineB = new StringBuffer(line);
            //This if block handles either last line or the scenario where in there's only one word in any sentence and hence no spaces
            if(j == unBalanced.size()-1 || !line.contains(" ")){
                int tempSpaces = maxWidth - lineB.length();
                while(tempSpaces > 0){
                    lineB.append(" ");
                    tempSpaces --;
                }
                balanced.add(lineB.toString());
                continue;
            };
            // The following block checks for each character and appends 1 space during each loop
            //If there are still spaces left at the end of the String, again start from beggining and append spaces after each word
            while(numSpaces > 0){
                int i = 0;
                while(i < lineB.length() - 1){
                    if( lineB.charAt(i) == ' ' && lineB.charAt(i+1) != ' '){
                        lineB.insert(i+1, ' ');
                        i++;
                        numSpaces --;
                        if(numSpaces == 0) break;
                    }
                    i++;
                }
            }
            balanced.add(lineB.toString());
        }

        return balanced;
    }
}