算法代码：查找数组中第i小的元素

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
#include <string.h>
using namespace std;

void swap(int *a, int *b)
{
	int temp;
	temp = *a;
	*a = *b;
	*b = temp;
}

int Partition(int A[], int p, int r)//将A[r]作为参考值，来划分数组，左边小于，右边大于（本来为快速排序的一部分）
{
	int x = A[r];
	int i = p-1;
	for(int j = p; j < r; j ++)
		if(A[j] <= x)
		{
			i++;
			swap(A[i],A[j]);
		}
	swap(A[i+1],A[r]);

	return i+1;
}

int Randomized_Partition(int A[], int p, int r)
{
	srand((unsigned)time(NULL)); 
	int i = (rand() % (r-p+1))+ p;//获取[p,r]之间的随机数
	swap(A[r], A[i]);
	return Partition(A, p, r);
}

int Randomized_Select(int A[], int p, int r, int i)
{
	if(p == r)
	{
		return A[p];
	}
	int q = Randomized_Partition(A, p, r);
	int k = q - p + 1;
	if(i == k)
		return A[q];
	else if(i < k)
		return Randomized_Select(A, p, q-1, i);
	else
		return Randomized_Select(A, q + 1, r, i - k);
}

int main()
{
	int T, i = 1, n, a[100];
	freopen("in.txt","r",stdin);
	//freopen("out.txt","w",stdout);
	cin >> T;
	n = T;

	while(T--)
	{
		cin>>a[i];
		i++;
	}

	cout<<Randomized_Select(a,1,8,5);

	fclose(stdin);
	//fclose(stdout);

	return 0;
}#include <iostream>
#include <stdio.h>
#include