Search for a Value in Linked List in DSA C - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this linked list search code?

Given the linked list and search function below, what will be printed when searching for value 3?

DSA C

typedef struct Node {
    int data;
    struct Node* next;
} Node;

#include <stdio.h>
#include <stdlib.h>

int search(Node* head, int val) {
    Node* current = head;
    while (current != NULL) {
        if (current->data == val) {
            return 1;
        }
        current = current->next;
    }
    return 0;
}

int main() {
    Node* head = malloc(sizeof(Node));
    head->data = 1;
    head->next = malloc(sizeof(Node));
    head->next->data = 2;
    head->next->next = malloc(sizeof(Node));
    head->next->next->data = 3;
    head->next->next->next = NULL;

    if (search(head, 3)) {
        printf("Found\n");
    } else {
        printf("Not Found\n");
    }
    return 0;
}

A Found

B Runtime Error

C Compilation Error

D Not Found

💡 Hint

Trace the linked list nodes and check if the value 3 exists.

The linked list contains nodes with values 1, 2, and 3. The search function returns 1 when it finds the value 3, so 'Found' is printed.

❓ Predict Output

intermediate

What is the output when searching for a value not in the list?

What will the program print when searching for value 5 in the linked list below?

DSA C

typedef struct Node {
    int data;
    struct Node* next;
} Node;

#include <stdio.h>
#include <stdlib.h>

int search(Node* head, int val) {
    Node* current = head;
    while (current != NULL) {
        if (current->data == val) {
            return 1;
        }
        current = current->next;
    }
    return 0;
}

int main() {
    Node* head = malloc(sizeof(Node));
    head->data = 10;
    head->next = malloc(sizeof(Node));
    head->next->data = 20;
    head->next->next = malloc(sizeof(Node));
    head->next->next->data = 30;
    head->next->next->next = NULL;

    if (search(head, 5)) {
        printf("Found\n");
    } else {
        printf("Not Found\n");
    }
    return 0;
}

A Found

B Compilation Error

C Not Found

D Segmentation Fault

💡 Hint

Check if 5 is present in the list nodes.

The linked list contains 10, 20, and 30. Since 5 is not in the list, the search returns 0 and prints 'Not Found'.

🔧 Debug

advanced

What error does this linked list search code cause?

What error will occur when running this code?

DSA C

typedef struct Node {
    int data;
    struct Node* next;
} Node;

#include <stdio.h>

int search(Node* head, int val) {
    Node* current = head;
    while (current->next != NULL) {
        if (current->data == val) {
            return 1;
        }
        current = current->next;
    }
    return 0;
}

int main() {
    Node node3 = {3, NULL};
    Node node2 = {2, &node3};
    Node node1 = {1, &node2};

    if (search(&node1, 3)) {
        printf("Found\n");
    } else {
        printf("Not Found\n");
    }
    return 0;
}

A No error, prints Found

B Infinite loop

C Compilation Error

D Segmentation Fault

💡 Hint

Look at the loop condition and what happens when current is the last node.

The loop condition stops when current->next is NULL, so it never checks the last node's data. If the value is in the last node, it is missed. Also, if the value is not found, current becomes NULL and accessing current->next causes a segmentation fault.

🧠 Conceptual

advanced

Why is the loop condition 'while(current != NULL)' preferred in linked list search?

Choose the best reason why 'while(current != NULL)' is used instead of 'while(current->next != NULL)' in linked list search.

A It prevents memory leaks in the linked list.

B It ensures the last node is checked for the value.

C It makes the code run faster by skipping the last node.

D It avoids the need to initialize the head pointer.

💡 Hint

Think about whether the last node's data is checked.

Using 'while(current != NULL)' ensures every node, including the last, is checked. Using 'while(current->next != NULL)' skips the last node, possibly missing the value.

🚀 Application

expert

What is the output after searching for value 7 in this linked list?

Given the linked list created dynamically and the search function, what will be printed when searching for value 7?

DSA C

#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
    int data;
    struct Node* next;
} Node;

Node* createNode(int val) {
    Node* newNode = malloc(sizeof(Node));
    newNode->data = val;
    newNode->next = NULL;
    return newNode;
}

int search(Node* head, int val) {
    Node* current = head;
    while (current != NULL) {
        if (current->data == val) {
            return 1;
        }
        current = current->next;
    }
    return 0;
}

int main() {
    Node* head = createNode(5);
    head->next = createNode(7);
    head->next->next = createNode(9);

    if (search(head, 7)) {
        printf("Found\n");
    } else {
        printf("Not Found\n");
    }
    return 0;
}

A Found

B Not Found

C Memory Leak Detected

D Segmentation Fault

💡 Hint

Check if the value 7 is in any node's data.

The linked list nodes contain 5, 7, and 9. The search finds 7 in the second node and returns 1, printing 'Found'.