sumparts.cpp

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

struct Node {
    int val;
    Node*next=0;
};

Node* nn(int d){
    return new Node{d};
}

Node* insert(Node* head, int d) {
    if (!head) return nn(d);
    Node* t=head;
    while (t->next){
        t=t->next;
    }
    t->next=nn(d);
    return head;
}

void display(Node*head){
    while(head){cout<<head->val<<" ";head=head->next;}
    cout<<endl;
}

Node* insertNum(Node* left, Node* right, int num) {
    Node* prev = left;
    for (auto c : to_string(num)) {
        left->val = c-'0';
        prev = left;
        left = left->next;
    }
    return prev;
}

Node* sumParts(Node* head) {
    if (!head || !head->next) return head;
    Node* cur = head;
    int sum = 0;
    while (cur && cur->val != 0) {
        sum += cur->val;
        cur = cur->next;
    }
    if (cur) {
        Node* rest = sumParts(cur->next);
        cur = insertNum(head, cur, sum);
        cur->next = rest;
    }
    return head;
}

int main(){
    Node*head=0;
    vector<int>nums={0,1};
    for(int i:nums)head=insert(head,i);
    display(head);
    head = sumParts(head);
    display(head);
}