344. Reverse String

 

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"]

 

这道题没什么难度,直接从两头往中间走,同时交换两边的字符即可,参见代码如下:

 

解法一:

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

 

我们也可以用 swap 函数来帮助我们翻转:

 

解法二:

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

 

Github 同步地址:

https://github.com/grandyang/leetcode/issues/344

 

类似题目:

Reverse Words in a String II

Reverse Words in a String

Reverse Vowels of a String 

Reverse String II

 

参考资料:

https://leetcode.com/problems/reverse-string/

https://leetcode.com/problems/reverse-string/discuss/80935/Simple-C%2B%2B-solution

https://leetcode.com/problems/reverse-string/discuss/80937/JAVA-Simple-and-Clean-with-Explanations-6-Solutions

 

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