LeetCode #6

What I’ve Learned

First, We can append length of array by digits = new int[digits.length + 1];

Disclaimer

My LeetCode is free plan. I am posting just the free algorithms for now on. Also, I am using JAVA to code.

58. Length of Last Word

My Solution

In Java, there is a method that splits with the given character. When we use list.split(), it returns with list form. It’s simple but, there are faster way I think.

class Solution {
    public int lengthOfLastWord(String s) {
    	String[] list = s.split(" ");
        return list[list.length - 1].length();
    }
}

Solution

This solution is faster. It uses pointer to check if it’s whitespace or not.

class Solution {
    public int lengthOfLastWord(String s) {
        int count =0;
        int idx = s.length()-1;

        for(int i = s.length()-1; i>=0; i--) {
            idx = i;
            if(!Character.isWhitespace(s.charAt(i))) {
                break;
            }
        }

        for(int i = idx; i >= 0; i--) {
            if(Character.isWhitespace(s.charAt(i))) {
                break;
            }
            count++;
        }
        return count;
    }
}

66. Plus One

My Solution

I thought there is no way to append another value in list. So, I’ve thought of using ArrayList. It worked, but problem was with appending another. In case of 99, you need to append 1.

class Solution {
    public int[] plusOne(int[] digits) {
    	digits[digits.length -1] += 1;
    	ArrayList<Integer> arr = new ArrayList<>();
    	for(int i = 0; i < digits.length; i++) {
    		arr.add(digits[i]);    	
    	}
    	for(int i = digits.length -1; i>0; i--) {
    		if(arr.get(i) == 10) {
    			arr.set(i, 0);
    			arr.set(i-1, arr.get(i-1) + 1);
    		}
    	}
    	System.out.print(arr);
    	return digits;
    }
}

Solution

It’s simple, fast. Using for loop, adding 1 to increase the amount. Approach was similar but, I wasn’t smart enough to use this algorithm

class Solution {
    public int[] plusOne(int[] digits) {
        for(int i = digits.length -1; i>=0; i--){
    	  if(digits[i] < 9){
            digits[i]++;
            return digits;
        }
        digits[i] = 0;
    }

    digits = new int[digits.length + 1];
    digits[0] = 1;
    return digits;
    }
}