# C Exercises: Pair in a linked list whose sum is equal to a given value

## C Singly Linked List : Exercise-38 with Solution

Write a C program to find a pair in a singly linked list whose sum is equal to a given value.

**Sample Solution:**

**C Code:**

```
#include<stdio.h>
#include <stdlib.h>
struct Node {
int data;
struct Node* next;
};
// Function to create a new node
struct Node* newNode(int data) {
struct Node* node = (struct Node*) malloc(sizeof(struct Node));
node->data = data;
node->next = NULL;
return node;
}
void pairSum(struct Node *head, int sum) {
struct Node *first = head;
struct Node *second = NULL;
int flag = 0;
while (first != NULL && first->next != NULL) {
second = first->next;
while (second != NULL) {
if ((first->data + second->data) == sum) {
printf("(%d,%d) ", first->data, second->data);
flag = 1;
}
second = second->next;
}
first = first->next;
}
if(flag==0)
printf("Pair not found.\n");
}
// Function to print a linked list
void displayList(struct Node* head) {
while (head) {
printf("%d ", head->data);
head = head->next;
}
printf("\n");
}
int main() {
struct Node* head = newNode(1);
head->next = newNode(2);
head->next->next = newNode(3);
head->next->next->next = newNode(4);
head->next->next->next->next = newNode(5);
head->next->next->next->next->next = newNode(6);
head->next->next->next->next->next ->next = newNode(7);
printf("Original singly linked list:\n");
displayList(head);
int s = 4;
printf("\nFind a pair whose sum is equal to 4:\n");
pairSum(head, s);
s = 11;
printf("\n\nFind a pair whose sum is equal to 11:\n");
pairSum(head, s);
s = 5;
printf("\n\nFind a pair whose sum is equal to 5:\n");
pairSum(head, s);
s = 14;
printf("\n\nFind a pair whose sum is equal to 14:\n");
pairSum(head, s);
return 0;
}
```

Sample Output:

Original singly linked list: 1 2 3 4 5 6 7 Find a pair whose sum is equal to 4: (1,3) Find a pair whose sum is equal to 11: (4,7) (5,6) Find a pair whose sum is equal to 5: (1,4) (2,3) Find a pair whose sum is equal to 14: Pair not found.

**Flowchart : **

**C Programming Code Editor:**

**Previous:** Delete all elements greater than x from a linked list.

**Next:** Interleave elements of two linked lists alternatively.

**What is the difficulty level of this exercise?**

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