与或

60 分

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int MAXN = 200000;
int n, k;
int a[MAXN + 5];
// 初始是 now，从 pos 开始，x 个 &，y 个 |， 
int cal(int now, int pos, int x, int y)
{
	for(int i=0;i<x;i++)
		now = now & a[pos+i];
	for(int i=0;i<y;i++)
		now = now | a[pos+x+i];
	return now;
}
signed main()
{
	cin >> n >> k;
	for(int i = 1; i <= n; i++)
		cin >> a[i];
	int xx = n - k - 1, yy = k; 
	int ans = cal(a[1], 2, xx, yy);
	cout << ans << "\n"; 
	int now = a[1];
	for(int i = 2; i <= n; i++)
	{ 
		if (yy > 0 && cal(now|a[i], i+1, xx, yy - 1) == ans)
		{
			// a[i] 使用 |
			yy --;
			now |= a[i]; 
			cout << "|"; 	
		}
		else
		{
			now &= a[i];
			xx --;
			cout << "&";
		}
		
	}
	return 0;
}

100 分

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int MAXN = 200000;
int n, k;
int a[MAXN + 5];
// a[1]~a[i] 在 2^j 有几个 1 
int cnt1[MAXN+5][65]; 
// 初始是 now，从 pos 开始，x 个 &，y 个 |， 
int cal(int now, int pos, int x, int y)
{
	int tempX = 0;
	int tempY = 0;
	for(int i=0;i<60;i++){
		int nowX = cnt1[pos+x-1][i]-cnt1[pos-1][i];
		if(nowX == x)
			tempX |= 1LL<<i;
		int nowY = cnt1[pos+x+y-1][i]-cnt1[pos+x-1][i];
		if(nowY > 0)
			tempY |= 1LL<<i;
	}
	now &= tempX;
	now |= tempY; 
	return now;
}
signed main()
{
	cin >> n >> k;
	for(int i = 1; i <= n; i++)
	{ 
		cin >> a[i];
		for(int j=0;j<60;j++)
			if(a[i]&(1LL<<j))
				cnt1[i][j] = cnt1[i-1][j] + 1;
			else
				cnt1[i][j] = cnt1[i-1][j];
	}
	int xx = n - k - 1, yy = k; 
	int ans = cal(a[1], 2, xx, yy);
	cout << ans << "\n"; 
	int now = a[1];
	for(int i = 2; i <= n; i++)
	{ 
		if (yy > 0 && cal(now|a[i], i+1, xx, yy - 1) == ans)
		{
			// a[i] 使用 |
			yy --;
			now |= a[i]; 
			cout << "|"; 	
		}
		else
		{
			now &= a[i];
			xx --;
			cout << "&";
		}
		
	}
	return 0;
}