CServer Side ProgrammingProgramming

Here we will see how to add 1 with a number stored into a linked list. In the linked list, each digit of the numbers is stored. If the number is 512, then it will be stored like below −

512 = (5)-->(1)-->(2)-->NULL

We are providing the list into the increment function. That will return another list after adding 1 with it. Here we are using the C++ STL linked list. Let us see the algorithm to bet better idea.

## Algorithm

#### incrementList(l1)

Begin
carry := 1
res := an empty list
for each node n from l1, scan from last to first, do
item := (l1.item + carry) mod 10
insert item at the beginning of res
carry := (l1.item + carry) / 10
done
if carry is not 0, then
add carry at the beginning of res
end if
return res
End

## Example

#include<iostream>
#include<list>
using namespace std;
list<int> incListNum(list<int> l1){
list<int>::reverse_iterator it1 = l1.rbegin();
list<int> result;
int carry = 1; //this 1 will be added
while(it1 != l1.rend()){
result.push_front((*it1 + carry) % 10);
carry = (*it1 + carry) / 10;
it1++;
}
if(carry != 0){
result.push_front(carry);
}
return result;
}
list<int> numToList(int n){
list<int> numList;
while(n != 0){
numList.push_front(n % 10);
n /= 10;
}
return numList;
}
void displayListNum(list<int> numList){
for(list<int>::iterator it = numList.begin(); it != numList.end();
it++){
cout<<*it;
}
cout << endl;
}
int main() {
int n1 = 9999;
list<int> n1_list = numToList(n1);
list<int> res = incListNum(n1_list);
cout << "The number: "; displayListNum(n1_list);
cout << "Result: "; displayListNum(res);
}

## Output

The number: 9999
Result: 10000