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StringStream in C++ for Decimal to Hexadecimal and back

  • Difficulty Level : Expert
  • Last Updated : 09 May, 2018

Stringstream is stream class present in C++ which is used for doing operations on a string. It can be used for formatting/parsing/converting a string to number/char etc.
Hex is an I/O manipulator that takes reference to an I/O stream as parameter and returns reference to the stream after manipulation.
Here is a quick way to convert any decimal to hexadecimal using stringstream:




// CPP program to convert integer to
// hexadecimal using stringstream and
// hex I/O manipulator.
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
    int i = 942;
    stringstream ss;
    ss << hex << i;
    string res = ss.str();
    cout << "0x" << res << endl; // this will print 0x3ae
    return 0;
}

Output:

0x3ae

If we want to change hexadecimal string back to decimal you can do it by following way:




// CPP program to convert hexadecimal to
// integer using stringstream and
// hex I/O manipulator.
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
    string hexStr = "0x3ae";
    unsigned int x;
    stringstream ss;
    ss << std::hex << hexStr;
    ss >> x;
    cout << x << endl; // this will print 942
    return 0;
}

Output:

942
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