13. Oracle

Role	Senior MTS, Sustenance Engineering
Profile	C, Linux, Multi threading

13.1. Round 1

Date	2024-02-14T11:00:08+0530

// global variable int
// 2 threads checking global variables & print Odd, Even

int num = 0; // initial value

pthread_cond_variable_t cv;
pthread_mutex_t mx;
pthread_lock_t lock;

void *print_odd(void *)
{
	pthread_lock_lock(lock, mx);
	while (pthread_cond_wait()) {
		if (num % 2 == 0) continue; // if even then wait
		printf("%d\n", num++);
		pthread_cond_notify();
	}
	pthread_lock_unlock(lock, mx);
}

void *print_even(void *)
{
	pthread_lock_lock(mx);
	while (pthread_cond_wait() && num) {
		if (num % 2 != 0) continue; // if odd then wait
		printf("%d\n", num++);
		pthread_cond_notify();
	}
	pthread_lock_unlock(mx);
}

// why condition variable is used?
while (!condition) { // uses cpu
	sleep(1);
}
// do some task

int main()
{
	pthread_t t1, t2;
	t1 = pthread_create(print_odd, NULL);
	t2 = pthread_create(print_even, NULL);
	t1.join();
}

// output
// 0 - t2 print_even
// 1 - t1 print_odd
// 2 - t2 print_even
// 3 - t1 print_odd
// 4 - t2 print_even

// WAP delete middle node of single linked list

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

    // odd:  1 -> 2 -> 3 -> 4 -> 5, delete 3
    // even: 1 -> 2 -> 3 -> 4, delete 2
    Node *
    delete_mid_node(Node *head)
{
	Node *temp = head;
	Node *fast = temp, *slow = temp;
	Node *prev = NULL;

	if (!temp) return NULL;
	if (!temp->next) {
		free(temp);
		return NULL;
	}

	while (fast->next && fast->next->next) {
		fast = fast->next->next;
		prev = slow;
		slow = slow->next;
	}
	prev->next = slow->next;
	free(slow);
	return head;
}

int main()
{
	Node *list = insert_list(1);
	list = delete_mid_node(list); // list is NULL
	return 0;
}

13.2. Round 2

Date

TBD

// Oracle round 2

#include <stdio.h>

// 5, 6, 7, 8, 1, 2, 3

int find_num(int arr[], int size, int num)
{
	// TC: O(n)
	int p = 0;
	for (int i = 0; i < size - 1; i++) {
		if (num > arr[i + 1]) {
			p = i;
			break;
		}
	}

	// TC: O(log n)
	int b = 0, e = p;
	int mid = (e - b) / 2;
	while (b < e) {
		if (num == arr[mid])
			return mid;
		else if (num > arr[mid]) {
			b = mid;
		} else if (num < arr[mid]) {
			e = mid;
		}
		mid = (e - b) / 2;
	}
}

// 5, 6, 7, 8, 1, 2, 3
// num: 2

int find_num(int arr[], int size, int num)
{
	// TC: O(log n)
	int b = 0, e = 0, p = 0;
	int mid = (e - b) / 2;

	// 5, 6, 7, 8, 1, 2, 3
	while (b < e) {
		if (num == arr[mid])
			return mid;
		else if (num > arr[mid]) {
			if (arr[b] < num) e = mid;
		} else if (num < arr[mid]) {
			if (arr[e] > num) b = mid;
		}
		mid = (e - b) / 2;
	}
}

int main()
{
	printf("Hello World");

	return 0;
}