418. Sentence Screen Fitting

Given a rows x cols screen and a sentence represented as a list of strings, return the number of times the given sentence can be fitted on the screen.

The order of words in the sentence must remain unchanged, and a word cannot be split into two lines. A single space must separate two consecutive words in a line.

 

Example 1:

Input: sentence = ["hello","world"], rows = 2, cols = 8
Output: 1
Explanation:
hello---
world---
The character '-' signifies an empty space on the screen.

Example 2:

Input: sentence = ["a", "bcd", "e"], rows = 3, cols = 6
Output: 2
Explanation:
a-bcd- 
e-a---
bcd-e-
The character '-' signifies an empty space on the screen.

Example 3:

Input: sentence = ["i","had","apple","pie"], rows = 4, cols = 5
Output: 1
Explanation:
i-had
apple
pie-i
had--
The character '-' signifies an empty space on the screen.

public class Solution {
    public int wordsTyping(String[] sentence, int rows, int cols) {
        String s = String.join("_", sentence) + "_";
        int len = s.length();
        int count = 0;
        int[] map = new int[len];
        for (int i = 1; i < len; ++i) {
            // if charAt(i) == '_', which means we saved an extra space
            map[i] = s.charAt(i) == '_' ? 1 : map[i-1] - 1;
        }
        for (int i = 0; i < rows; ++i) {
            count += cols;
            count += map[count % len];
        }
        return count / len;
    }
}

    public int wordsTyping(String[] sentence, int rows, int cols) {
        String s = String.join(" ", sentence) + " ";
        int start = 0;
        int length = s.length();
        for (int i = 0; i < rows; i++) {
            start += cols;
            if (s.charAt(start % length) == ' ') {
                start++;
            } else {
                while (start >= 0 && s.charAt(start % length) != ' ') {
                    start--;
                }
                start++;
            }
        }
        
        return start / length;
    }