Educational Codeforces Round 161 (Rated for Div. 2)

A.

不满足一个即可

// Problem: A. Tricky Template
// Contest: Codeforces - Educational Codeforces Round 161 (Rated for Div. 2)
// URL: https://codeforces.com/contest/1922/problem/0
// Memory Limit: 256 MB
// Time Limit: 2000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include<bits/stdc++.h>
#define eps 1e-5
#define INF 1e9
using namespace std;
typedef long long ll;
const int N = 2e6 + 9;
int a[N];
void Lan(){
	int n;
	cin>>n;
	string a,b,c;
	cin>>a>>b>>c;
	for(int i=0;i<n;i++){
		if(a[i]==b[i] && a[i]!=c[i]){
			cout<<"YES"<<'\n';
			return;
		}else if(a[i]!=b[i] && a[i]!=c[i] && b[i]!=c[i]){
			cout<<"YES"<<'\n';
			return;
		}
	}
	cout<<"NO"<<'\n';
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	int q;
	cin>>q;
	while (q--) {
		Lan();
	}
	return 0;
}

B.

1.x=y=z;C(3,n)

2.x<y=z;C(2,n)*(前缀和)

// Problem: B. Forming Triangles
// Contest: Codeforces - Educational Codeforces Round 161 (Rated for Div. 2)
// URL: https://codeforces.com/contest/1922/problem/B
// Memory Limit: 256 MB
// Time Limit: 2000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include<bits/stdc++.h>
#define eps 1e-5
#define INF 1e9
using namespace std;
typedef long long ll;
const int N = 2e6 + 9;
ll a[N];
void Lan(){
	int n;
	cin>>n;
	for(int i=0;i<=n;i++){
		a[i]=0;
	}
	for(int i=1;i<=n;i++){
		int x;
		cin>>x;
		a[x]++;
	}
	ll ans=0;
	ll tot=0;
	for(int i=0;i<=n;i++){
		ans+=a[i]*(a[i]-1)*(a[i]-2)/6;
		ans+=a[i]*(a[i]-1)/2*tot;
		tot+=a[i];
	}
	cout<<ans<<'\n';	
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	int q;
	cin>>q;
	while (q--) {
		Lan();
	}
	return 0;
}

C.

处理一下最近城市

然后前缀和计算

// Problem: C. Closest Cities
// Contest: Codeforces - Educational Codeforces Round 161 (Rated for Div. 2)
// URL: https://codeforces.com/contest/1922/problem/C
// Memory Limit: 256 MB
// Time Limit: 2000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include<bits/stdc++.h>
#define eps 1e-5
#define INF 1e9
using namespace std;
typedef long long ll;
const int N = 2e6 + 9;
ll a[N],l[N],r[N];
void Lan(){
	int n;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	for(int i=1;i<n;i++){
		int rdis=a[i+1]-a[i];
		int ldis=a[i]-a[i-1];
		if(rdis<ldis || i==1){
			r[i]=1;
		}else{
			r[i]=rdis;
		}
	}
	for(int i=2;i<=n;i++){
		int rdis=a[i+1]-a[i];
		int ldis=a[i]-a[i-1];
		if(rdis>ldis || i==n){
			l[i]=1;
		}else{
			l[i]=ldis;
		}
	}
	l[n+1]=0;
	for(int i=1;i<=n;i++){
		r[i]+=r[i-1];
	}
	for(int i=n;i>=1;i--){
		l[i]+=l[i+1];
	}
	int m;
	cin>>m;
	while(m--){
		int x,y;
		cin>>x>>y;
		if(x<=y){
			cout<<r[y-1]-r[x-1]<<'\n';
		}else{
			cout<<l[y+1]-l[x+1]<<'\n';
		}
	}	
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	int q;
	cin>>q;
	while (q--) {
		Lan();
	}
	return 0;
}