reverse c string

CC150 1.1 reverse c string

void swap(char &a, char &b){
    a = a^b;
    b = a^b;
    a = a^b;
}

void reverse(char *s){
    if (!s) return s;
    char * p = s;
    char * q = s;
    while(q) ++q;
    --q;//move from null to the last char
    while(p<q){
    swap(*p++,*q--);
    //std::swap(str[i], str[j])
    }
}

class Solution {
public:
    string reverseString(string s) {
        int left = 0;
        int right = s.size()-1;
        while(left<right){
            swap(s[left++],s[right--]);
        }
        return s;
    }
};//16/07/04

• Note:a & b must be different to use XOR swap
• REF:
• https://en.wikipedia.org/wiki/XOR_swap_algorithm
• http://en.cppreference.com/w/cpp/language/operator_precedence
• http://stackoverflow.com/questions/3825668/c-c-checking-for-null-pointer