#leetcode#Text Justification

L家高频题....

毫无头绪， 学习了code ganker大神的解法，做了适当注释

package TextJustification;
import java.util.*;

public class Solution {
	public ArrayList<String> fullJustify(String[] words, int L) {
		ArrayList<String> res = new ArrayList<String>();
		if (words == null || words.length == 0)
			return res;
		int count = 0;
		int last = 0;
		for (int i = 0; i < words.length; i++) {
			if (count + words[i].length() + (i - last) > L) {
				int spaceNum = 0;
				int extraNum = 0;
				if (i - last - 1 > 0) {
					spaceNum = (L - count) / (i - last - 1); // (L - count) is the number of spaces to be inserted. (i - 1) is the index of last string in the current row, (i - 1 - last) is how many intervals to put space, so (L - count) / (i - last - 1) is how many spaces to insert in each interval of strings    
					extraNum = (L - count) % (i - last - 1); // calculate if one more space need to be inserted into the left intervals
				}
				StringBuilder str = new StringBuilder();
				for (int j = last; j < i; j++) {
					str.append(words[j]);
					if (j < i - 1) {// see if current string is the last string in the current row. (i - 1) is the index of last string, because words[i] makes current length > L
						for (int k = 0; k < spaceNum; k++) {
							str.append(" ");
						}
						if (extraNum > 0) {
							str.append(" ");
						}
						extraNum--;
					}
				}
				for (int j = str.length(); j < L; j++) {  // sometimes spaceNum, extraNum are both zero, so you need to insert spaces after the string.
					str.append(" ");
				}
				res.add(str.toString());
				count = 0;
				last = i;
			}
			count += words[i].length();
		}
		StringBuilder str = new StringBuilder();
		for (int i = last; i < words.length; i++) {
			str.append(words[i]);
			if (str.length() < L)
				str.append(" ");
		}
		for (int i = str.length(); i < L; i++) {
			str.append(" ");
		}
		res.add(str.toString());
		return res;
	}
}