Merge Sort

Medium Sorting Algorithms

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Problem Statement

Write a C program to implement Merge Sort to sort an array of integers in ascending order.

Input Format

First line: N. Second line: N space-separated integers.

Output Format

Print the sorted array separated by a space.

Constraints

1 <= N <= 1000

Sample Input

5
38 27 43 3 9

Sample Output

3 9 27 38 43

Explanation

Divide and conquer algorithm that splits array and merges sorted halves.

Starter Code

#include <stdio.h>

void merge(int arr[], int l, int m, int r) {
    int n1 = m - l + 1;
    int n2 = r - m;
    int L[n1], R[n2];
    for (int i = 0; i < n1; i++) L[i] = arr[l + i];
    for (int j = 0; j < n2; j++) R[j] = arr[m + 1 + j];
    int i = 0, j = 0, k = l;
    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) arr[k++] = L[i++];
        else arr[k++] = R[j++];
    }
    while (i < n1) arr[k++] = L[i++];
    while (j < n2) arr[k++] = R[j++];
}

void mergeSort(int arr[], int l, int r) {
    if (l < r) {
        int m = l + (r - l) / 2;
        mergeSort(arr, l, m);
        mergeSort(arr, m + 1, r);
        merge(arr, l, m, r);
    }
}

int main() {
    int n;
    if (scanf("%d", &n) == 1) {
        int arr[n];
        for (int i = 0; i < n; i++) scanf("%d", &arr[i]);
        mergeSort(arr, 0, n - 1);
        for (int i = 0; i < n; i++) {
            printf("%d", arr[i]);
            if (i < n - 1) printf(" ");
        }
        printf("n");
    }
    return 0;
}

Limits

Time Limit: 1s
Memory Limit: 256MB

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