Leetcode skimming ---202

subject ： Write a function , Its function is to invert the input string . Input string as character array s Given in the form of . Do not allocate extra space to another array , You have to modify the input array in place 、 Use O(1) To solve this problem .

Input ：s = ["h","e","l","l","o"]

Output ：["o","l","l","e","h"]

Method 2 ： Double pointer

class Solution {
public:
    void reverseString(vector<char>& s) {
        int n = s.size();
        for (int left = 0, right = n -1; left < right; left++, right--) {
            swap(s[left], s[right]);
        }
    }
};

Complexity analysis

Time complexity ：O(N)

Spatial complexity ：O(1)