Leetcode: Reverse Words in a String (8ms) (string)(two pointers)

PROBLEM:


https://leetcode.com/problems/reverse-words-in-a-string/


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Searching a word from right to left, using two pointers to mark the location of a word. using another string to temporally store the result.


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//8ms

class Solution {

public:

       void reverseWords(string &s) {

              int n = s.size(), l = n - 1, r = n - 1;

              string res;

              while (l>-1){

                     int i = l;

                     //looking for non-space char

                     while (i>-1 && s[i] == ' ')i--;

                     r = i;

                     if (i == -1)break;//all leading char are ' '.

                     //looking for space. Note: put i>-1 ahead of s[i]!=' ';

                     while (i>-1 && s[i] != ' ')i--;

                     l = i + 1;

                     res.append(s, l, r - l + 1);

                     res.push_back(' ');

                     l = i - 1;

                     r = l;

              }

              //check input and check tmp result and remove final space

              if(n!=0 && res.size()!=0)res.erase(res.size()-1,1);

              s = res;

       }

};