AcWing 786. 第k个数

题目链接

https://www.acwing.com/problem/content/788/

思路

先用一种 n l o g 2 n nlog_2n nlog2​n的排序算法排序，然后输出第k个元素即可

代码

#include
using namespace std;
#define ll long long
#define mod 1000000009
#define endl "\n"
#define PII pair
ll ksm(ll a,ll b) {
	ll ans = 1;
	for(;b;b>>=1LL) {
		if(b & 1) ans = ans * a % mod;
		a = a * a % mod;
	}
	return ans;
}

ll lowbit(ll x){return -x & x;}

const int N = 2e6+10;
int n,a[N];

void mysort(int a[],int l,int r) {
	if(l >= r) return;
	int x = a[l + r >> 1],i = l - 1,j = r + 1;
	while(i