Codeforces Round 923 (Div. 3)

A. Make it White

#include<bits/stdc++.h>
using namespace std;
void solve(){
	int a,b,n;
	string s;
	cin>>n>>s;
	for(int i=0;i<n;i++){
		if(s[i]=='B'){
			a=i;
			break;
		}
	}
	for(int i=n-1;i>=0;i--){
		if(s[i]=='B'){
			b=i;
			break;
		}
	}
	cout<<b-a+1<<"\n";
}
int main(){
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	int t=1;
	cin>>t;
	for(int i=1;i<=t;i++)solve();
	return 0;
} 

B. Following the String 暴力

#include<bits/stdc++.h>
using namespace std;
const int N=2e5+10;
int a[N];
void solve(){
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i];
	map<char,int>mp;
	for(int i=1;i<=n;i++){
		int x=a[i];
		for(char j='a';j<='z';j++){
			if(mp[j]==x){
				cout<<j;
				mp[j]++;
				break;
			}
		}
	}
	cout<<"\n";
}
int main(){
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	int t=1;
	cin>>t;
	for(int i=1;i<=t;i++)solve();
	return 0;
} 

C. Choose the Different Ones! 贪心+思维

#include<bits/stdc++.h>
using namespace std;
void solve(){
	int n,m,k;
	cin>>n>>m>>k;
	map<int,int>mp1;
	map<int,int>mp2;
	for(int i=1;i<=n;i++){
		int x;
		cin>>x;
		if(x<=k)mp1[x]++;
	}
	for(int i=1;i<=m;i++){
		int x;
		cin>>x;
		if(x<=k)mp2[x]++;
	}
	int t1=0,t2=0,t3=0;
	for(int i=1;i<=k;i++){
		if(mp1[i]&&!mp2[i])t1++;
		else if(!mp1[i]&&mp2[i])t2++;
		else if(mp1[i]&&mp2[i])t3++;
		else{
			cout<<"NO\n";
			return;
		}
	}
	for(int i=0;i<=t3;i++){
		if(t1+i==t2+(t3-i)&&t1+i==k/2){
			cout<<"YES\n";
			return;
		}
	}
	cout<<"NO\n";
}
int main(){
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	int t=1;
	cin>>t;
	for(int i=1;i<=t;i++)solve();
	return 0;
} 

D. Find the Different Ones!

有点像dp // a[i]代表了与a[i]不同值的a[j]的最近下表j且j< i

#include<bits/stdc++.h>
using namespace std;
const int N=2e5+10;
int a[N];
int b[N];
void solve(){
	int n;
	cin>>n;
	int c=0;
	for(int i=1;i<=n;i++)cin>>a[i];
	for(int i=2;i<=n;i++){
		if(a[i-1]!=a[i]){
			c=i-1;
		}
		b[i]=c;
	}
	int q;
	cin>>q;
	for(int i=1;i<=q;i++){
		int l,r;
		cin>>l>>r;
		if(b[r]<l){
			cout<<-1<<" "<<-1<<"\n";
		}else{
			cout<<b[r]<<" "<<r<<"\n";
		}
	}
	cout<<"\n";
}
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	int t;
	cin>>t;
	for(int i=1;i<=t;i++)solve();
	return 0;
}