s=input()
ans=0
k=0
for i in range(len(s)-1,-1,-1):
    ans+=int(s[i])*2**k
    k+=1
print(ans)

s=input()
ans=0
for i in range(len(s)):
    ans=ans+int(s[i])*(2**(len(s)-1-i))
print(ans)

s=input()
ans=0
for i in range(0,len(s)):
    ans=int(s[i])+ans*2
print(ans)

print(int(input(),2))

孩子们，用无敌的公式代码杀穿进制转换吧！

我只能说

ps：即a进制转b进制，此题a=2，b=10

#include<bits/stdc++.h>
using namespace std;
#define Maxn 1000005
//#define int long long

string x;
int a,b,l=0,m=0;
long long c;
char ans[Maxn];

signed main()
{
	a=2,b=10;
	cin>>x;
	for(int i=x.size()-1;i>=0;i--)
	{
		if(x[i]>='0'&&x[i]<='9')
			c+=(x[i]-'0')*pow(a,m);
		else
			c+=(x[i]-'A'+10)*pow(a,m);
		m++;
	}
	while(c)
	{
		if(c%b<10)
			ans[l]=char(c%b+'0');
		else
			ans[l]=char((c%b)%10+'A');
		l++;
		c=(c-(c%b))/b;
	}
	for(int i=l-1;i>=0;i--)
		cout<<ans[i];
	return 0;
}

s=input()
ans=0
k=0
for i in range(len(s)):
    ans=ans*2+int(s[i])
    
print(ans)

s=input()
ans=0
for i in range(len(s)):
    ans=ans*2+int(s[i])
print(ans)

x=input()
s=0
for i in range(len(x)):
    s+=int(x[i])*2**(len(x)-1-i)
print(s)