leetcode

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58. Length of Last Word

题目

Given a string s consisting of some words separated by some number of 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.

题目大意

给你一个字符串 s，由若干单词组成，单词前后用一些空格字符隔开。返回字符串中最后一个单词的长度。单词 是指仅由字母组成、不包含任何空格字符的最大子字符串。

解题思路

• 先从后过滤掉空格找到单词尾部，再从尾部向前遍历，找到单词头部，最后两者相减，即为单词的长度。

代码

package leetcode

func lengthOfLastWord(s string) int {
	last := len(s) - 1
	for last >= 0 && s[last] == ' ' {
		last--
	}
	if last < 0 {
		return 0
	}
	first := last
	for first >= 0 && s[first] != ' ' {
		first--
	}
	return last - first
}