poj 4088:集合运算

poj 4088:集合运算

题目：（至于4089，那个问题做过，使用归并思想，所以没有写）

10 5
1  3  8 20 2
9 10 12  8 9 

8

解题方案

借用于快速排序思想，查找第K小元素

代码

#include <iostream>
#include <fstream>
using namespace std;

void main_solution();
void read_data( int *& data,int &n,int &k );
int min_k(int *data,int s,int e,int k);

int main()
{
	main_solution();
	system("pause");
	return 0;
}

void read_data( int *& data,int &n,int &k )
{
	ifstream reader;
	reader.open( "data.txt" );
	reader>>n;
	reader>>k;
	data = new int[n];
	for(int i=0;i<n;i++)
	{
		reader>>data[i];
	}
	reader.close();
}

int min_k(int *data,int s,int e,int k)
{
	int  t = s;
	int another = e;
	while(t != another)
	{
		if( t < another )
		{
			if( data[t] <= data[another] )
				another --;
			else
			{
				int d = data[another];
				data[another] = data[t];
				data[t] = d;

				d = another;
				another = t;
				t = d;
			}
		}
		else
		{
			if( data[t] >= data[another] )
				another ++;
			else
			{
				int d = data[another];
				data[another] = data[t];
				data[t] = d;

				d = another;
				another = t;
				t = d;
			}
		}
	}

	if( k == t-s+1 )
		return data[t];
	else if( k < t-s+1 )
		return min_k(data,s,t-1,k);
	else return min_k(data,t+1,e,k - (t-s+1));

}

void main_solution()
{
	int * data;
	int n;
	int k;
	read_data(data,n,k);
	cout<<min_k(data,0,n-1,k)<<endl;
}