归并排序（C语言实现）

#include <stdio.h>

#include <stdlib.h>

void merge(int A[], int p, int q, int r);

void merge_sort(int A[], int p, int r);

//主函数

int main() 

{
int a[8] = {2, 4, 5, 7, 1, 2, 3, 6};
int i = 0;
merge_sort(a, 0, 7);
for (i = 0; i < 8; i++)
{
printf("%d ", a[i]);
}
printf("\n");

return 0;
}

//归并

void merge(int A[], int p, int q, int r)

{
int i, j, k;
int n1 = q - p + 1;
int n2 = r - q;
int * L = (int *)malloc(sizeof(int) * n1);
int * R = (int *)malloc(sizeof(int) * n2);
if (L == NULL || R == NULL) 
{
printf("memory allocation is failed");
exit(-1);
}

for (i = 0; i < n1; i++) 
{
L[i] = A[p + i];
}
for (j = 0; j < n2; j++) 
{
R[j] = A[q + j + 1];
}

i = 0;
j = 0;
k = p;
while (i < n1 && j < n2) 
{
if (L[i] < R[j]) 
{
A[k++] = L[i++];
}
else
{
A[k++] = R[j++];
}
}
while (i < n1)
{
A[k++] = L[i++];
}
while (j < n2)
{
A[k++] = R[j++];
}

if (L != NULL && R != NULL)
{
free(L);
free(R);
}

}

//归并排序

void merge_sort(int A[], int p, int r)

{
int q;
if (p < r)
{
q = (p + r) / 2;
merge_sort(A, p, q);
merge_sort(A, q+1, r);
merge(A, p, q, r);
}

}