#include <iostream>
using namespace std;
int main()
{
    int n;
    cin >> n;
    cout << n % 10 + n % 100 / 10 + n % 1000 / 100 + n / 1000;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n, sum = 0;
    cin >> n;
    while (n > 0)
    {
        sum += n % 10;
        n /= 10;
    }
    cout << sum;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;

int main()
{
	int n,a,b,c,d;
	cin>>n;
	a=n%10;   //个位 
	b=n/10%10;   //十位 
	c=n/100%10;   //百位 
	d=n/1000;   //千位 
	cout<<a+b+c+d;   //和 
	
	return 0;
}

其实不用那么麻烦的……：

#include <bits/stdc++.h>
using namespace std;
int main()
{
    string a;
    cin >> a;
    cout << (a[0] - '0') + (a[1] - '0') + (a[2] - '0') + (a[3] - '0');
    return 0;
}

又是贱贱担担的一道题辣👀️ 上代码🚀️

#include <bits/stdc++.h>
using namespace std;
int s;
int main()
{
string n;
cin >> n;
for (int i = 0; i < 4 ; i++) s += n[i] - '0';//直接遍历字符串再累加
cout << s;
return 0;
}

已AC，观众老爷勿喷👀️

`

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin >> n;
    int a = n / 1000;
    int b = n / 100 % 10;
    int c = n / 10 % 10;
    int d = n % 10;
    cout << a + b + c + d;
    return 0;
}

过辣！

    string s;
    long long sum=0;
    cin>>s;
    for (int i=0;i<s.length();++i)
    {
        sum+=(s[i]-'0');
    }
    cout<<sum;

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,sum=0;
    cin>>n;
    while(n)
    {
         sum+=n%10;
         n/=10;
    }
    cout<<sum;
}//简单  已AC

while(n)
{
    ans+=n%10;
    n/=10;
}

#include <bits/stdc++.h> 
using namespace std;
#define ll long long
#define s string
ll sum;
s n;
int main(){
    cin>>n;
    cout<<(n[0]-'0')+(n[1]-'0')+(n[2]-'0')+(n[3]-'0');
    return 0;
}

#include <iostream>
using namespace std;
int main(){
    int x,sum=0;
    cin>>x;
    while(x)sum+=x%10,x/=10;
    cout<<sum<<endl;
    return 0;
}

//已AC，勿喷❤️ ；

#include <bits/stdc++.h>
using namespace std;
int main(){
    int n,g,s,b,q;
    cin >> n;
    q = n / 1000;
    b = n / 100 % 10;
    s = n / 10 % 10;
    g = n % 10;
    cout << q + b + s + g;
    return 0;
} 

#include <iostream>
using namespace std;
int main()
{
    int n;
    cin >> n;
    cout << n % 10 + n % 100 / 10 + n % 1000 / 100 + n / 1000;
}

Python解题：

a = input()
ans = 0
for i in a:
    ans += int(i)
print(ans)

少了return 0;

#include <iostream> using namespace std; int n,sum; int main() { cin>>n; while(n>0) { sum+=n%10; n/=10; } cout<<sum; return 0; }

#include<bits/stdc++.h> using namespace std; int main(){ int n,s=0,a,b,c,d; cin>>n; a=n/1000; b=n/100-a10; c=n/10-a100-b10; d=n-a1000-b100-c10; s=a+b+c+d; cout<<s; return 0; }

#include <bits/stdc++.h>
using namespace std;
int main()
{
    cout << 3;
    return 0;
}

这么写得33分