c++ 奇怪的错误与十进制到二进制转换器

Question

I'm a complete newbie to C++ programming. I've been given the task to code decimal to hexadecimal,octal,binary conversion.I have encountered errors in the "binario" function, when I enter a decimal number greater than 1000 the function gives me a result as a nonsense random numbers.

int binario(int n){
    int r,val=0, i=1;
    while (n>0) {
      val=val+(n%2*i);
      n=n/2;
      i=i*10;
   }
   return val;
}

Answer 1

In C++, the maximum size for int is 4 bytes which means from -2,147,483,648 to 2,147,483,647. Binary of 1024 is 10000000000 and it's more than int range. This is why you see the error. You can use your function for numbers less than 1024. I suggest you using string for your function(you have to include string header):

string binario(int n){
    string bin = "";
    while (n>0) {
      bin += to_string(n%2);
      n=n/2;
   }
   //reverse string
   for (int i = 0; i < bin.size() / 2; i++) {
    swap(bin[i], bin[bin.size() - i - 1]); 
   } 

   return bin;
}