10亿数中找出最大1000个数的算法C实现（简化版）

此处主要采用堆排序来实现。

typedef int ElementType;

typedef struct
{
	ElementType *r;
	int length;
}SqList;

#define N 20
#define M 10

void HeapAdjust(SqList *L, int s, int m)
{
	int temp, j;
	temp = L->r[s];
	
	for(j = 2 * s; j <= m; j *= 2)
	{
		if(j < m && L->r[j] > L->r[j + 1])
			j++;
		
		if(temp <= L->r[j])
			break;
			
		L->r[s] = L->r[j];
		s = j;
	}
	
	L->r[s] = temp;
}

SqList* searchLarge(ElementType A[])
{
	int i, j;
	
	SqList *L;
	
	L = (SqList *)malloc(sizeof(SqList));	
	L->length = M;
	
	L->r = (ElementType *)malloc(N * sizeof(ElementType));
	
	for(i = 1; i <= M; i++)
	{
 		L->r[i] = A[i];
	}
	
	for(i = L->length/2; i > 0; i--)
	{
		HeapAdjust(L, i, L->length);
	}
	
	for(i = M + 1; i <= N; i++)
	{
		if(L->r[1] > A[i])
			continue;
		else
		{
			L->r[1] = A[i];
			for(j = L->length/2; j > 0; j--)
			{
				HeapAdjust(L, 1, L->length);
			}
		}
	}
	
	return L;
}

int main(int argc, char **agrv)
{
	int A[N + 1];
	int i;
	for(i = 1; i <= 20; i++)
	{
		A[i] = (i + N - M + 12) % 20;
	}
	
	printf("Data set is as follows:\n");
	
	for(i = 1; i <= N; i++)
	{
        printf("%d ", A[i]);
    }
    printf("\n");
	
	SqList *L;
	
	L = searchLarge(A);
	
	printf("The 10 largest numbers are:\n");
	
	for(i = 1; i <= L->length; i++)
	{
		printf("%d ", L->r[i]);
	}
	
	printf("\n");
	
	return 0;
}typedef int ElementType;