左右双指针即可
void reverseString(vector& s) { for (int left = 0, right = s.size() - 1; left < right; ++left, --right) swap(s[left++], s[right--]); }

左右双指针即可
void reverseString(vector& s) { for (int left = 0, right = s.size() - 1; left < right; ++left, --right) swap(s[left++], s[right--]); }