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Question

Formatted question description: https://leetcode.ca/all/58.html

Given a string s consisting of words and spaces, return the length of the last word in the string.

A word is a maximal substring consisting of non-space characters only.

 

Example 1:

Input: s = "Hello World"
Output: 5
Explanation: The last word is "World" with length 5.

Example 2:

Input: s = "   fly me   to   the moon  "
Output: 4
Explanation: The last word is "moon" with length 4.

Example 3:

Input: s = "luffy is still joyboy"
Output: 6
Explanation: The last word is "joyboy" with length 6.

 

Constraints:

• 1 <= s.length <= 104
• s consists of only English letters and spaces ' '.
• There will be at least one word in s.

Algorithm

Preprocess the input string first, remove the spaces at the beginning and the end, and then use a counter to accumulate the length of the non-space string, and clear the counter when it encounters a space.

Code

• Java
• C++
• Python
• Go
• TypeScript
• Javascript
• Php
• RenderScript
• C#

• 
  public class Length_of_Last_Word {
  
  	public class Solution_no_extra_space { // one scan
  	    public int lengthOfLastWord(String s) {
  	        if (s == null || s.length() == 0) {
  	            return 0;
  	        }
  
  	        int count = 0;
  	        for (int i = s.length() - 1; i >= 0; i--) {
  
  	            if (count == 0 && s.charAt(i) != ' ') { // skip spaces
  	                count++;
  	            } else if (count != 0 && s.charAt(i) == ' ') {
  	                break;
  	            } else if (('a' <= s.charAt(i) && s.charAt(i) <= 'z') || ('A' <= s.charAt(i) && s.charAt(i) <= 'Z')) {
  	                count++;
  	            }
  	        }
  
  	        return count;
  
  	    }
  	}
  
  	public class Solution {
  	    public int lengthOfLastWord(String s) {
  
  	        if (s == null || s.length() == 0) {
  	            return 0;
  	        }
  
  	        String[] array = s.split(" "); // @note: if input is string with spaces “ “, the array length is 0
  
  	        if (array.length == 0) {
  	            return 0;
  	        } else {
  	            return array[array.length - 1].length();
  	        }
  
  	    }
  	}
  
  }
  
  ############
  
  class Solution {
      public int lengthOfLastWord(String s) {
          int i = s.length() - 1;
          while (i >= 0 && s.charAt(i) == ' ') {
              --i;
          }
          int j = i;
          while (j >= 0 && s.charAt(j) != ' ') {
              --j;
          }
          return i - j;
      }
  }
  

• // OJ: https://leetcode.com/problems/length-of-last-word/
  // Time: O(N)
  // Space: O(1)
  class Solution {
  public:
      int lengthOfLastWord(string s) {
          int i = s.size() - 1;
          while (i >= 0 && s[i] == ' ') --i;
          int j = i;
          while (i >= 0 && s[i] != ' ') --i;
          return j - i; 
      }
  };
  

• class Solution:
      def lengthOfLastWord(self, s: str) -> int:
          i = len(s) - 1
          while i >= 0 and s[i] == ' ':
              i -= 1
          j = i
          while j >= 0 and s[j] != ' ':
              j -= 1
          return i - j
  
  ############
  
  class Solution(object):
    def lengthOfLastWord(self, s):
      """
      :type s: str
      :rtype: int
      """
      if len(s) == 0:
        return 0
      s = s.split()
      if len(s) > 0:
        return len(s[-1])
      return 0
  
  

• func lengthOfLastWord(s string) int {
  	i := len(s) - 1
  	for i >= 0 && s[i] == ' ' {
  		i--
  	}
  	j := i
  	for j >= 0 && s[j] != ' ' {
  		j--
  	}
  	return i - j
  }
  

• function lengthOfLastWord(s: string): number {
      s = s.trimEnd();
      const n = s.length;
      const index = s.lastIndexOf(' ');
      if (index !== -1) {
          return n - index - 1;
      }
      return n;
  }
  
  

• /**
   * @param {string} s
   * @return {number}
   */
  var lengthOfLastWord = function (s) {
      let i = s.length - 1;
      while (i >= 0 && s[i] === ' ') {
          --i;
      }
      let j = i;
      while (j >= 0 && s[j] !== ' ') {
          --j;
      }
      return i - j;
  };
  
  

• class Solution {
      /**
       * @param String $s
       * @return Integer
       */
      function lengthOfLastWord($s) {
          $count = 0;
          while ($s[strlen($s) - 1] == " ") {
              $s = substr($s, 0, -1);
          }
          while (strlen($s) != 0 && $s[strlen($s) - 1] != " ") {
              $count++;
              $s = substr($s, 0, -1);
          }
          return $count;
      }
  }
  

• impl Solution {
      pub fn length_of_last_word(s: String) -> i32 {
          let s = s.trim_end();
          let n = s.len();
          for (i, c) in s.char_indices().rev() {
              if c == ' ' {
                  return (n - i - 1) as i32;
              }
          }
          n as i32
      }
  }
  
  

• public class Solution {
      public int LengthOfLastWord(string s) {
          int i = s.Length - 1;
          while (i >= 0 && s[i] == ' ') {
              --i;
          }
          int j = i;
          while (j >= 0 && s[j] != ' ') {
              --j;
          }
          return i - j;
      }
  }
  

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