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josephus.c
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josephus.c
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#include <stdio.h>
#include <stdlib.h>
// Structure to represent a node in the circular queue
struct QueueNode {
int data;
struct QueueNode* next;
};
// Structure to represent the circular queue
struct CircularQueue {
struct QueueNode* front;
struct QueueNode* rear;
};
// Function to create an empty circular queue
struct CircularQueue* createQueue() {
struct CircularQueue* queue = (struct CircularQueue*)malloc(sizeof(struct CircularQueue));
queue->front = queue->rear = NULL;
return queue;
}
// Function to enqueue a person into the circular queue
void enqueue(struct CircularQueue* queue, int data) {
struct QueueNode* newNode = (struct QueueNode*)malloc(sizeof(struct QueueNode));
newNode->data = data;
if (queue->rear == NULL) {
newNode->next = newNode; // If the queue is empty, set the next pointer to itself
queue->front = queue->rear = newNode;
} else {
newNode->next = queue->front; // Make the new node point to the front
queue->rear->next = newNode; // Update the rear's next to point to the new node
queue->rear = newNode; // Update the rear to the new node
}
}
// Function to dequeue and eliminate every k-th person until one person remains
int josephus(struct CircularQueue* queue, int k) {
struct QueueNode* current = queue->front;
struct QueueNode* previous = NULL;
while (queue->front->next != queue->front) {
int count = 1;
while (count < k) {
previous = current;
current = current->next;
count++;
}
if (previous != NULL) {
previous->next = current->next;
queue->front = previous->next;
} else {
queue->rear = NULL;
queue->front = NULL;
}
free(current);
current = queue->front;
}
return current->data;
}
int main() {
int n, k;
printf("Enter the number of people: ");
scanf("%d", &n);
printf("Enter the counting interval (k): ");
scanf("%d", &k);
struct CircularQueue* queue = createQueue();
for (int i = 1; i <= n; i++) {
enqueue(queue, i);
}
int survivor = josephus(queue, k);
printf("The last person standing is at position: %d\n", survivor);
free(queue); // Free allocated memory
return 0;
}