병합정렬

#include <stdio.h>
#include <stdlib.h>
void printArr(int *a, int start, int end)
{
    int i;
 
    for (i = start; i <= end; i++)
        printf("%3d", a[i]);
    printf("\n");
}
void merge(int* a, int start, int mid, int end)
{
    int index1 = start, index2 = mid + 1, index3 = start, i;
    int* tmp;
 
    tmp = (int*)malloc(sizeof(int) * (end + 1));
 
    while (index1 <= mid && index2 <= end)
    {
        if (a[index1] <= a[index2])
        {
            tmp[index3] = a[index1];
            index1++;
        }
        else
        {
            tmp[index3] = a[index2];
            index2++;
        }
 
        index3++;
    }
 
    while (index1 <= mid)
        tmp[index3++] = a[index1++];
    while (index2 <= end)
        tmp[index3++] = a[index2++];
 
    for (i = start; i <= end; i++)
        a[i] = tmp[i];
}
void mergeSort(int* a, int start, int end)
{
    int mid;
 
    if (start < end) {
        mid = (start + end) / 2;
 
        mergeSort(a, start, mid);
        mergeSort(a, mid + 1, end);
 
        merge(a, start, mid, end);
        printArr(a, start, end);
    }
}
int main(void)
{
    int a[] = { 10, 50, 69, 27, 40, 72, 59, 21, 96, 4 };
    int i;
 
    mergeSort(a, 0, 9);
 
    printArr(a, 0, 9);
}

 

결과: