Member Avatar for ghadahelal

hi,
i have a program which read the input stream as a character then it transdforms this charcters to integers

in the input stream there is ^, ex , x^2
how can i deal with.

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  • Latest Post Latest Post by William Hemsworth

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Short summary and a robust fix for the "x^y" input problem (builds on 's note that atoi expects a C-string and that casting a char gives the character code).

If each operand is a single digit, convert a digit character to its numeric value by subtracting the ASCII digit zero ('0'). Always validate with std::isdigit and cast the argument to unsigned char before calling it to avoid UB (std::isdigit). For anything larger than one digit (e.g., 12^3) read the whole token and parse around the caret; use std::stoi/std::stoll for conversion so you get proper error handling ().

Practical parsing and integer-power example:

std::string token;
if (std::cin >> token) {
  auto pos = token.find('^');
  if (pos == std::string::npos) { /* handle malformed input */ }

  std::string left = token.substr(0, pos);
  std::string right = token.substr(pos + 1);

  try {
    long long base = std::stoll(left);
    int exp = std::stoi(right);

    auto int_pow = [](long long b, int e) {
      long long r = 1;
      while (e > 0) {
        if (e & 1) r *= b;
        b *= b;
        e >>= 1;
      }
      return r;
    };

    long long result = int_pow(base, exp);
    std::cout << result << '\n';
  } catch (const std::exception& ex) {
    /* handle invalid number or overflow */
  }
}

Troubleshooting notes: std::pow returns floating point and can introduce rounding; use integer exponentiation for integer math or check/round results if using pow (std::pow). Watch for overflow on large bases/exponents and handle negative exponents (they produce fractions) separately.

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Member Avatar for ghadahelal

another Question:

when i use atoi(char) , there is an error

Member Avatar for ghadahelal

in the follwing program i'm trying to read a characters and transform them to integers .
the input will be in this form x^y
but i become an error


char x,y,z;
int i,k,res;

cin>>x>>y>>z;

if( isdigit(x))
i= atoi(x);

if(isdigit(z))
k= atoi(z);

if(y=='^')
res= pow(i,k);

cout<<"res="<<res;

Member Avatar for William Hemsworth

that is because the function atoi isn't for converting a char to an int, it converts a string (char array) to an int. If you want to convert a char to an int you need to type cast. for example:

char a = 'z';
int num = (int) a;
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