C++ program to convert binary to decimal

Here is a C++ program to convert binary to decimal. Here are the different methods to convert binary to decimal like using recursion.
How to convert binary to decimal .

Method 1 : C++ program to convert binary to decimal

#include<iostream>
#include<math.h>
using namespace std;
int main()
{
    long decimal=0,rem,num,temp=1;
    cout<<"Enter the number in binary ";
    cin>>num;
    temp=num;
    for(int i=0;num>0;i++)
    {
        rem=num%10;
        num/=10;
        decimal+=rem*pow(2,i);
    }
    cout<<"Decimal equivalent "<<decimal;
    return 0;
}

Method 2 : C++ program to convert binary to decimal using recursion

#include<iostream>
#include<math.h>
using namespace std;
int deci(int n,int i)
{
    if(n==0)
        return 0;
    return (n%10)*pow(2,i)+deci(n/10,i+1);
}
int main()
{
    int num;
    cout<<"Enter Binary number : ";
    cin>>num;
    cout<<"Decimal equivalent : "<<deci(num,0);
    return 0;
}

Method 3 : Another C++ program to convert binary to decimal

#include<iostream>
#include<math.h>
#include<string.h>
using namespace std;
int main()
{
    int decimal=0,lt;
    char num[30];
    cout<<"Enter the number in binary ";
    cin>>num;
    lt=strlen(num)-1;
    for(int i=lt;i>=0;i--)
        decimal+=(num[i]-48)*pow(2,lt-i);
    cout<<"Decimal equivalent "<<decimal;
    return 0;
}

Method 4 : C++ program to convert decimal to binary using function

#include<iostream>
#include<math.h>
#include<string.h>
using namespace std;
void binary(char *a,int lt)
{
    int decimal=0;
    for(int i=lt;i>=0;i--)
        decimal+=(a[i]-48)*pow(2,lt-i);
    cout<<"Decimal equivalent "<<decimal;
}
int main()
{
    int lt;
    char num[30];
    cout<<"Enter the number in binary ";
    cin>>num;
    lt=strlen(num)-1;
    binary(num,lt);
    return 0;
}