0058. Length of Last Word¶
Given a string s consists of some words separated by spaces, return the length of the last word in the string. If the last word does not exist, return 0.
A word is a maximal substring consisting of non-space characters only.
Example 1:
Input: s = "Hello World"
Output: 5
Example 2:
Input: s = " "
Output: 0
Constraints:
1 <= s.length <= 104sconsists of only English letters and spaces' '.
Analysis¶
Our goal is to find the first word that is either between two spaces or the left char is a space. In order to do so, we just need to check from the rightmost pos to left, once we find a character that is not space, we update our counter. If the counter is greater than one and we meet another space, that means we have already found our target string, and we can just return the counter. The worst case is when the whole world is space OR no space at all -- in such case, we need to iterate the entire string from the end to the start.
- Time: O(n)
- Space: O(1)
Code¶
class Solution {
public:
int lengthOfLastWord(string s) {
int res = 0;
for (int i = s.size() - 1; i >= 0; --i) {
if (res > 0 && s[i] == ' ') return res;
if (s[i] != ' ') res ++;
}
return res;
}
};