蓝桥杯 2022 A组C题

简单

#include<bits/stdc++.h>
using namespace std;
const int maxn = 200001;
int a[maxn];
long long sum[maxn];
int main()
{
	std::ios::sync_with_stdio(false);
	std::cin.tie(0);
	int n;
	long long total = 0;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> a[i];
		total += a[i];
	}
	sum[0] = total;
	for (int i = 1; i <= n; i++)
	{
		sum[i] = sum[i - 1] - a[i - 1];
	}
	long long ans = 0;
	for (int i = 0; i < n; i++)
		ans += a[i] * sum[i + 1];
	cout << ans;
}

中等

#include<bits/stdc++.h>
#define endl "\n"
using namespace std;
const int maxn = 1e5 + 10;
int yihuo[maxn];

map<long long, int>num_index;
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);

	int n, m;
	long long x;
	cin >> n >> m >> x;
	for (int i = 1; i <= n; i++)
	{
		long long t;
		cin >> t;
		yihuo[i] = max(yihuo[i - 1], num_index[t ^ x]);
		num_index[t] = i;
	}
	for (int i = 0; i < m; i++)
	{
		int a, b;
		cin >> a >> b;
		if (yihuo[b] >= a)
			cout << "yes" << endl;
		else
			cout << "no" << endl;
	}
}

划重点

1. 加速

ios_base::sync_with_stdio(false);
cin.tie(0);

2. 加速

#define endl "\n"

3. a^b=c，则a^c=b