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"]
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1）
这个是水题，不过我打算用递归来解决它
C++代码：
class Solution {
public:
void reverseString(vector<char>& s) {
helper(s,0,s.size()-1);
}
void helper(vector<char>& s,int start,int end){
if(start >= end){
return;
}
char tmp = s[start];
s[start] = s[end];
s[end] = tmp;
helper(s,start+1,end-1); //是两端往中心靠的递归
}
};
2）
这个可以用双指针。
C++代码：
class Solution {
public:
void reverseString(vector<char>& s) {
int i = ,j = s.size() - ;
while(i < j){
swap(s[i],s[j]);
i++;
j--;
}
}
};