Question

Write a c++ routine that returns true if two elements in a singly linked list of integers add up to a given target (similar to the two sum problem 1). Your function should return true and print the individual numbers, or return false.

Examples:

- If your list is: 1 → 3 → 4 → 14 → 5 and your target is 8, then you will return true and print: 3, 5 (since 3 + 5 = 8).

- If your list is: 1 → 3 → 4 → 14 → 5 and your target is 11, then you will just return false.

For this, you will need to implement the linked list class we discussed in class (for the purpose of this assignment, implementing the constructor, the add function, and the print function, should suffice). You can also instead use the STL list/iterator to implement your function.

Answer 1

In case of any queries, please revert back.

I will be implementing the linked list class for complete explanation.

#include <bits/stdc++.h>
#define MAX 10000
using namespace std;
  
//the Node of the Linked List
struct LinkedNode {
int value;
struct LinkedNode* next;
};
  
//Push to the Linked List as per Lifo order
void pushNode(struct LinkedNode** header, int new_value)
{
//we define the new node from the memory and allocate data and next
struct LinkedNode* new_node = (struct LinkedNode*)malloc(sizeof(struct LinkedNode));
new_node->value = new_value;
new_node->next = (*header);
//Move header to next node for continuation of linked list
(*header) = new_node;
}
  
//Checks if the Sum Exists in the list or not
bool pairSumCheck(struct LinkedNode* header, int sumValue)
{ //We define a set.
unordered_set<int> setA;
//Now, we allocate header to the ptr Node
struct LinkedNode* ptr = header;
//Performing the loop for the next nodes
while (ptr != NULL) {
//lets save value for each node
int currentValue = ptr->value;
// if sumValue-currentValue is equal to pointer value ie. last element of setA
// we exit the loop as we have found the sum.
if (setA.find(sumValue - currentValue) != setA.end())
{
cout <<" true "<<currentValue << " " << sumValue - currentValue;
return true;
}
// else we insert he pointer value to the set
setA.insert(ptr->value);
//We move on to the next iteration
ptr = ptr->next;
}
  
return false;
}
  
int main()
{
//Declare the linked List
struct LinkedNode* headerOfList = NULL;
  
// add elements to the list
pushNode(&headerOfList, 1);
pushNode(&headerOfList, 3);
pushNode(&headerOfList, 4);
pushNode(&headerOfList, 14);
pushNode(&headerOfList, 5);
  
/* function to print the result*/
bool result = pairSumCheck(headerOfList, 8);
if (result == false)
cout << "false";
  
return 0;
}