1.1 Implement an algorithm to determine if a string has all unique characters. What if you cannot use additional data structures?

1.1.cpp

#include<iostream>

const unsigned NUM_CHAR = 256;

bool hasAllUniqueChar (std::string s)
{
    if (s.size() > NUM_CHAR) return false;
    
    // init array
    unsigned array[NUM_CHAR/sizeof(int)+1] = {};
    
    // check if the char has appeared
    for (auto c : s) {
        int idx = c/sizeof(int);
        unsigned flag = 1 << c%sizeof(int);
        if ((array[idx] & flag) != 0) return false;
        array[idx] |= flag;
    }
    return true;
}

int main(int argc, char *argv[])
{
    std::string s = "";
    std::cin >> s;
    std::cout << hasAllUniqueChar(s) << std::endl;
    return 0;
}