이것 저것 &

#include <stdio.h>
#define MAXSIZE 100000

const int LM = (int)100001;
int index[LM], temp[LM];

void mergesort(int s, int e, int* a, int* b) {

    //1. base condition
    if (s >= e)
        return;

    //2.divide
    int mid = (s + e) / 2;
    

    //3. conquer
    mergesort(s, mid, a, b);
    mergesort(mid + 1, e, a, b);

    //4. merge
    int i = s, j = mid + 1;
    for (int k = s; k <= e; k++) {

        if (i > mid)
            b[k] = a[j++];
        else if (j > e)
            b[k] = a[i++];
        else if (a[i] > a[j])
            b[k] = a[j++];
        else
            b[k] = a[i++];
    }

    //5. copy
    for (int k = s; k <= e; k++) {
        a[k] = b[k];
    }
}