Question

How do I covert a char from a sting that is made up of hex values into a long int, without using istringstream and istring in c++?

Answer 1

Solution:

c++ code

#include<bits/stdc++.h>
using namespace std;
long fun(string s){

long res=16,k=0,ans=0;

for(int i=s.length()-1;i>=0;i--){

//we are traversing string from right to left

if(s[i]>='0'&&s[i]<='9'){

ans+=pow(res,k)*(s[i]-'0');

}

else if(s[i]=='a'||s[i]=='b'||s[i]=='c'||s[i]=='d'||s[i]=='e'||s[i]=='f'){

//ascii value of W = 87 and a in hexadecimal is 10 and

//ascii value of a =97

ans+=pow(res,k)*(s[i]-'W');

}

else if(s[i]=='A'||s[i]=='B'||s[i]=='C'||s[i]=='D'||s[i]=='E'||s[i]=='F'){

//ascii value of char 7 is 55 and

//ascii value of char A is 65

ans+=pow(res,k)*(s[i]-'7');

}

k++;

}
}

int main(){

string s;

cout<<"Enter a hexadecimal string"<<endl;

cin>>s;//taking input

//calling fun function with argument input string

long res=fun(s);

cout<<"long int value is "<<res<<endl;
}

Screenshot of the code and output:

NOTE:

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