Problem

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.

Example1

Input: [“h”,“e”,“l”,“l”,“o”] Output: [“o”,“l”,“l”,“e”,“h”]

Example2

Input: [“H”,“a”,“n”,“n”,“a”,“h”] Output: [“h”,“a”,“n”,“n”,“a”,“H”]

Solution

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