数组第K小的元素

最新推荐文章于 2024-07-27 14:37:39 发布

原创最新推荐文章于 2024-07-27 14:37:39 发布 · 194 阅读

0 ·

CC 4.0 BY-SA版权

数据结构专栏收录该内容

14 篇文章

订阅专栏

本文深入探讨了快速排序和二分查找算法的实现细节，通过具体代码展示了如何运用这两种算法解决特定问题，如寻找数组中的第K个元素。

快排+二分

int getpart(int a[],int low,int high){
	if (low>high)
	{
		return -1;
	}
	int low_t = low;
	int high_t = high;
	int key = a[low];

	while (low < high)
	{
		while(low < high && a[high] >= key)
		{
			high--;
		}
		if (low<high)
		{
			a[low++] = a[high];
		}

		while(low < high && a[low] <= key)
		{
			low++;
		}
		if (low<high)
		{
			a[high--] = a[low];
		}
	}
	a[low] = key; //中轴
	return low;
}

int getKnum(int a[],int length,int k){
	if (length==0 || k>length)
	{
		return -1;
	}
	int start = 0;
	int end = length - 1;
	int index = getpart(a,start,end);

	while (index != k-1)
	{
		//中轴在目的元素的左边
		if (index > k-1)
		{
			 end = index - 1;
			 index = getpart(a,start,end);
		}
		else//中轴在目的元素的右边
		{
			start = index + 1;
			index = getpart(a,start,end);
		}
	}
	return a[index];
}
void main(){
	int a[] = {5,1,2,6,4,3,9,8,7,10};
	int k = 10;
	int len = sizeof (a)/4;
	int r = getKnum(a,len,k);
	printf("%d",r);

	while(1);
}

最小的K个数，不按排序输出

//不按顺序
int getKnums(int a[],int length,int k){
	if (length==0 || k>length)
	{
		return -1;
	}
	int start = 0;
	int end = length - 1;
	int index = getpart(a,start,end);

	while (index != k-1)
	{
		//中轴在目的元素的左边
		if (index > k-1)
		{
			end = index - 1;
			index = getpart(a,start,end);
		}
		else//中轴在目的元素的右边
		{
			start = index + 1;
			index = getpart(a,start,end);
		}
	}
	for (int i=0;i<k;i++)
	{
		printf("%d ",a[i]);
	}

	return a[index];
}