Well, the basic idea is very simple. Start from the tail of s and move backwards to find the first non-space character. Then from this character, move backwards and count the number of non-space characters until we pass over the head of s or meet a space character. The count will then be the length of the last word.
1 class Solution { 2 public: 3 int lengthOfLastWord(string s) { 4 int len = 0, tail = s.length() - 1; 5 while (tail >= 0 && s[tail] == ' ') tail--; 6 while (tail >= 0 && s[tail] != ' ') { 7 len++; 8 tail--; 9 } 10 return len; 11 } 12 };
