mergeSort.cpp

#include <iostream>
using namespace std;
void input(int a[], int &n){
    cin >> n;
    for (int i = 0; i < n; i++){
        cin >> a[i];
    }
}
void printArray(int a[], int n){
    for (int i = 0; i < n; i++){
        cout << a[i] << " ";
    }
}
void merge(int arr[], int l, int m, int r){
    int i, j, k;
    int n1 = m - l + 1;
    int n2 = r - m;
    int L[n1], R[n2];
    for (i = 0; i < n1; i++){
        L[i] = arr[l + i];
    }
    for (j = 0; j < n2; j++){
        R[j] = arr[m + 1 + j];
    }
    i = 0;
    j = 0;
    k = l;
    while (i < n1 && j < n2){
        if (L[i] <= R[j]){
            arr[k] = L[i];
            i++;
        } else {
            arr[k] = R[j];
            j++;
        }
        k++;
    }
    while (i < n1){
        arr[k] = L[i];
        i++;
        k++;
    }
    while (j < n2){
        arr[k] = R[j];
        j++;
        k++;
    }
}
void mergeSort(int a[], int l, int r){
    if(l < r){
        int m = l+(r-l)/2;
        mergeSort(a, l, m);
        mergeSort(a, m+1, r);
        merge(a, l, m, r);
    }
}
int a[100001];
int main(){
    int n;
    input(a, n);
    mergeSort(a, 0, n-1);
    printArray(a, n);
    cout << endl;
    return 0;
}