LeetCode 344. Reverse String

原题链接在这里：https://leetcode.com/problems/reverse-string/

题目：

Write a function that reverses a string. The input string is given as an array of characters char[].

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

Example 1:

Input: ["h","e","l","l","o"]
Output: ["o","l","l","e","h"]

Example 2:

Input: ["H","a","n","n","a","h"]
Output: ["h","a","n","n","a","H"]

题解：

Reverse string是常见题, string在Java中是primitive类型, 一旦生成不可改变.

But we have the array of char here. Then use two pointers. Remember to move pointer in while loop.

Time Complexity: O(s.length).

Space: O(1).

AC Java:

class Solution {
    public void reverseString(char[] s) {
        int l = 0;
        int r = s.length - 1;
        
        while(l < r){
            char temp = s[l];
            s[l] = s[r];
            s[r] = temp;
            
            l++;
            r--;
        }
    }
}

AC C++:

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

跟上Reverse String II, Reverse Vowels of a String.