SDU Open 2021 Fall 题解-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_62105443/article/details/126004998

补体记录： B D G H

B A+B

这道题虽然我的大致思路和题解差不多也是利用b的长度来处理但我处理枚举等能力太弱了根本不知道可以直接暴力枚举来统计答案结果就抛弃了这个想法导致浪费了几小时吃土


#include<bits/stdc++.h>
using namespace std;
#define int long long
int ans = 0;
int n;
int pow1(int a, int b)
{
	if (b == 0)
		return 1;
	int res = 1;
	while (b)
	{
		if (b & 1)
		{
			res = res * a;
		}
		a = a * a;
		b >>= 1;
	}
	return res;
}
signed main()
{
	cin >> n;

	int len = log10(n)+1;
//	cout << len << endl;
	for (int i = 1; i <=len; i++)
	{
		for (int j = 0; j <=i; j++)
		{
			for (int k = 0; k <= i; k++)
			{
				int p = pow1(2, j)*pow1(5, k);
				int l = pow1(10, i-1), r = min(n, pow1(10, i) - 1);
				ans += (r / p - (l - 1) / p);
			}
		}
	}
	cout << ans;
}

D：

这个构造题要是没对二进制有一定理解是写不出来的

#include<algorithm>
#include<set>
#include<string>
#include<cstring>
#include<iostream>
using namespace std;
#define int long long
const int maxn = 1e5 + 10;
void solve()
{
	set<int>s;
	while (s.size())
		s.erase(*s.begin());
	string now ;
	for (int i = 0; i <= 31; i++){
		cout << "+ " << i << endl;
		s.insert(i);
		cin >> now;
		if (now == "YES")
		{
			string ss;
			for (int j = 0; j < i; j++)
			{
				cout << "- " << j<<endl;
				cin >> ss;
				s.erase(j);
				if (ss == "NO")
				{
					cout << "! " << i - j << endl;
					cin >> ss;
				
					return;
				}
			}
	     }
	}
	for (int i = 1; i <= 32; i++)
	{
		int x = 32 * i + 31;
		cout << "+ " << x << endl;
		s.insert(x);
		cin >> now;
		if (now == "YES")
		{
			string ss;
			for (int j = 0; j <= 31; j++)
			{
				cout << "- " << j<<endl;
				cin >> ss;
				s.erase(j);
				if (ss == "NO")
				{
					cout << "! " << x - j << endl;
					cin >> ss;
					return;
				}
			}
		}
	}
}
signed main()
{
	int t;
	cin >> t;
	while (t--)
		solve();
}

G ：

#include<iostream>
#include<algorithm>
using namespace std;
#define int long long
const int maxn = 1e6 + 10;
const int mod = 1e9 + 7;
int dp[maxn][8];//dp[i][j]代表数字i 最大位数为j的方案数
signed main()
{
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++)
	{
		if (i >= 1)
		{

			if (i == 1)
			{
				dp[i][1] = 1;
			}
			else
			{
				dp[i][1] += dp[i - 1][1];
				dp[i][1] %= mod;
			}
		}
		 if (i >= 2)
		{
			if (i == 2)
			{
				dp[2][2] = 1;
			}
			else
			{
				dp[i][2] += dp[i - 2][1] + dp[i - 2][2];
				dp[i][2] %= mod;
			}
		}
		 if (i >= 3)
		 {
			 if (i == 3)
				 dp[3][3] = 1;
			 else
			 {
				 dp[i][3] += dp[i - 3][1] + dp[i - 3][2] + dp[i - 3][3];
				 dp[i][3] %= mod;
			 }
		 }
		 if (i >= 5)
		 {
			 if (i == 5)
				 dp[5][5] = 1;
			 else
			 {
				 dp[i][5] += dp[i - 5][1] + dp[i - 5][2] + dp[i - 5][5]+dp[i-5][3];
				 dp[i][5] %= mod;
			 }
	     }
		if (i >= 7)
		{
			if (i == 7)
				dp[7][7] = 1;
			else
			{
				dp[i][7] += dp[i - 7][7] + dp[i - 7][1] + dp[i - 7][2] + dp[i - 7][5]+dp[i-7][3];
				dp[i][7] %= mod;
			}
		}
	}
	int ans = 1;
	for (int i = 1; i <= 7; i++)
		(ans += dp[n][i]) %= mod;
	cout << ans;
}

H: 思路参考：middle（洛谷）

#include<iostream>
#include<algorithm>
using namespace std;
#define int long long
const int maxn = 3e5 + 10;
struct node
{
	int l, r;
	int pref_max, pref_min, sum, suff_max, suff_min;
}tree[maxn<<2];
int a[maxn], cnt[maxn];
int b[maxn];
void pushup(int rt){
	tree[rt].sum = tree[rt << 1].sum + tree[rt << 1 | 1].sum;
	tree[rt].pref_max = max(tree[rt << 1].pref_max, tree[rt << 1].sum + tree[rt << 1 | 1].pref_max);
	tree[rt].suff_max = max(tree[rt << 1 | 1].suff_max, tree[rt << 1 | 1].sum + tree[rt << 1].suff_max);
	tree[rt].pref_min = min(tree[rt << 1].pref_min, tree[rt << 1].sum + tree[rt << 1 | 1].pref_min);
	tree[rt].suff_min = min(tree[rt << 1 | 1].suff_min, tree[rt << 1 | 1].sum + tree[rt << 1].suff_min);
}
void build(int rt, int l, int r)
{
	tree[rt].l = l, tree[rt].r = r;
	if (l == r)
	{
		tree[rt].pref_max = tree[rt].pref_min = tree[rt].suff_max = tree[rt].suff_min = tree[rt].sum = b[l];
		return;
	}
	int mid = l + r >> 1;
	build(rt << 1, l, mid);
	build(rt << 1 | 1, mid + 1, r);
	pushup(rt);
}
void modify(int rt, int l, int r, int q, int v)//单点
{
	if (l == q && r == q)
	{
		tree[rt].pref_max = tree[rt].pref_min = tree[rt].suff_max = tree[rt].suff_min = tree[rt].sum = v;
		return;
	}
	int mid = l + r >> 1;
	if (q <= mid)
		modify(rt << 1, l, mid, q, v);
	else
		modify(rt << 1 | 1, mid + 1, r, q, v);
	pushup(rt);
}
int querysum(int rt, int l, int r, int ql, int qr)
{
	if (l == ql && r == qr)
		return tree[rt].sum;
	int mid = l + r >> 1;
	if (qr <= mid)
		return querysum(rt << 1, l, mid, ql, qr);
	else if (ql > mid)
		return querysum(rt << 1 | 1, mid + 1, r, ql, qr);
	else
	{
		int ret = querysum(rt << 1, l, mid, ql, mid);
		ret += querysum(rt << 1|1, mid + 1, r, mid + 1, qr);
		return ret;
	}
}
int queryprefmax(int rt, int l, int r, int ql, int qr)
{
	if (l == ql && r == qr)
		return tree[rt].pref_max;
	int mid = l + r >> 1;
	if (qr <= mid)
	{
		return queryprefmax(rt << 1, l, mid, ql, qr);
	}
	else if (ql > mid)
		return queryprefmax(rt << 1 | 1, mid + 1, r, ql, qr);
	else
	{
		int ret = queryprefmax(rt << 1, l, mid, ql, mid);
		int ret2 = querysum(rt << 1, l, mid, ql, mid) + queryprefmax(rt << 1 | 1, mid + 1, r, mid + 1, qr);
		return max(ret, ret2);
	}
}
int queryprefmin(int rt, int l, int r, int ql, int qr)
{
	if (l == ql && r == qr)
		return tree[rt].pref_min;
	int mid = l + r >> 1;
	if (qr <= mid)
		return queryprefmin(rt << 1, l, mid, ql, qr);
	else if (ql > mid)
		return queryprefmin(rt << 1 | 1, mid+1, r, ql, qr);
	else
	{
		int ret = queryprefmin(rt << 1, l, mid, ql, mid);
		int ret2 = querysum(rt << 1, l, mid, ql,mid) + queryprefmin(rt << 1 | 1, mid + 1, r, mid + 1, qr);
		return min(ret, ret2);
	}
}
int querysuffmax(int rt, int l, int r, int ql, int qr)
{
	if (l == ql && r == qr)
		return tree[rt].suff_max;
	int mid = l + r >> 1;
	if (qr <= mid)
	{
		return querysuffmax(rt << 1, l, mid, ql, qr);
	}
	else if (ql > mid)
		return querysuffmax(rt << 1 | 1, mid + 1, r, ql, qr);
	else
	{
		int ret = querysuffmax(rt << 1|1, mid+1,r, mid+1,qr);
		int ret2 = querysum(rt << 1|1, mid+1, r, mid+1, qr) + querysuffmax(rt << 1, l, mid,ql,mid);
		return max(ret, ret2);
	}
}
int querysuffmin(int rt, int l, int r, int ql, int qr)
{
	if (l == ql && r == qr)
		return tree[rt].suff_min;
	int mid = l + r >> 1;
	if (qr <= mid)
		return querysuffmin(rt << 1, l, mid, ql, qr);
	else if (ql > mid)
		return querysuffmin(rt << 1 | 1, mid + 1, r, ql, qr);
	else
	{
		int ret = querysuffmin(rt << 1|1, mid+1, r, mid+1, qr);
		int ret2 = querysum(rt << 1|1, mid+1, r, mid+1, qr) + querysuffmin(rt << 1 , l, mid,ql,mid);
		return min(ret, ret2);
	}
}
void solve(){
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++)
	{
		cin >> a[i];
		if (a[i] < 1)
			b[i] = -1;
		else if (a[i] == 1)
			b[i] == 0;
		else
			b[i] = 1;
		cnt[a[i]] = i;
	}
	build(1, 1, n);
	for (int i = 1; i <= n; i++)
	{
		//cout << i << endl;
			int preemax = 0, preemin = 0;
			int suffmax = 0, suffmin = 0;
			if (cnt[i] != 1)//代表前面有数
			{
				preemax = querysuffmax(1, 1, n, 1, cnt[i]-1);
				preemin =querysuffmin(1, 1, n, 1, cnt[i]-1);
			//1 左边是0
				if (preemin <= 0 && preemax >= 0)
				{
					cout << "y";
					modify(1, 1, n, cnt[i], -1);
					if(i!=n)
					modify(1, 1, n, cnt[i + 1], 0);
					continue;
				}
			}
			if (cnt[i] != n)//代表后面有数
			{
				suffmax =queryprefmax(1, 1, n, cnt[i]+1, n);
				suffmin =queryprefmin(1, 1, n, cnt[i]+1, n);
				if (suffmax >= 0 && suffmin <= 0)
				{
					cout << 'y';
					modify(1, 1, n, cnt[i], -1);
					if(i!=n)
					modify(1, 1, n, cnt[i + 1], 0);
					continue;
			  }
			}
			if (cnt[i] == n)//代表后米面没有数
			{
				if (preemax >= 0 && preemin <= 0)//代表前面有数
				{
					cout << 'y';
				}
				else
					cout << 'n';
			}
			else if (cnt[i] == 1)
			{
				if (suffmin <= 0 && suffmax >= 0)
				{
					cout << 'y';
				}
				else
					cout << 'n';
			}
			else
			{
				if (preemin <= -suffmin && preemax >= -suffmax)
				{
					cout << 'y';
				}
				else
					cout << "n";
			}
			modify(1, 1, n, cnt[i], -1);
			if(i!=n)
			modify(1, 1, n, cnt[i + 1], 0);
			//cout << endl;
	}
	cout <<'\n';
}
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);
	int t;
	cin >> t;
	while (t--)
		solve();
}