leetcode twopointers 344 revese string

THE

problem

achieve

Ideas

In this question, seeing the concept of reversal, left and right, we must want dichotomy and left and right double pointers. Since it is not a sorting issue, consider the left and right double pointers. Just apply the basic left and right pointer template.

• define left right
• get mid
• • while left >= mid
• • swap ;
• return

Summary and reflection

1. Note the boundary problem solved in mid = (0+ size())/2 and while(left<right). Together, they can handle arrays of singular or even length. The principle is easy to derive by pushing it by yourself.

Code

class Solution {
    
    
public:
   void reverseString(vector<char>& s) {
    
    
       int left = 0;
       int right = s.size();
       int mid = (left+right)/2;// pay attention into whether mid is correct. 
       while(left<right){
    
    
           swap(s,left,right);
           left++;
           right--;
       }
       
   }
   void swap(vector<char> &s,int left,int right){
    
    
       char temp = '\0';
       temp  = s[left];
       s[left] = s[right-1];
       s[right-1] = temp;
   }
};