Middle Node

Lab C Intermediate 20 points

Build a list from n integers and print the middle value using the slow/fast pointer technique (for even lengths, the second of the two middle values).

Input

Line 1: n. Line 2: n integers.

Output

One integer.

Example

Input

5
1 2 3 4 5

Output

Sample input available Sample output available

Editor

Hints

Move slow by one and fast by two; when fast reaches the end, slow is in the middle.

Solution explanation

The two-speed walk finds the middle in one pass without counting first.

Show solution

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

struct Node {
    int value;
    struct Node *next;
};

int main() {
    int n, x;
    struct Node *head = NULL, *tail = NULL;
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf("%d", &x);
        struct Node *node = malloc(sizeof(struct Node));
        node->value = x;
        node->next = NULL;
        if (head == NULL) head = node;
        else tail->next = node;
        tail = node;
    }
    struct Node *slow = head, *fast = head;
    while (fast != NULL && fast->next != NULL) {
        slow = slow->next;
        fast = fast->next->next;
    }
    printf("%d\n", slow->value);
    return 0;
}

Output

Answer