Codeforces Round 797 (Div. 3)

A - Print a Pedestal (Codeforces logo?)

#include "bits/stdc++.h"
using namespace std;

#define int long long 
#define endl '\n'
#define IOS ios::sync_with_stdio(0),cin.tie(0);
#define all(x) x.begin(),x.end()
#define pi pair<int,int> 
#define vi vector<int>

void solve()
{
	int n;
	cin>>n;
	int a=0,b=0,c=0;
    
	if(n%3==0){
		cout<<n/3<<" "<<n/3+1<<" "<<n/3-1<<endl;
	}
	else if (n%3==1){
		cout<<n/3<<" "<<n/3+2<<" "<<n/3-1<<endl;
	}
	else {
		cout<<n/3+1<<" "<<n/3+2<<" "<<n/3-1<<endl;
	}
	
	
	
	
	
}   
signed main()
{
	IOS
	int t;
	cin>>t;
	while(t--){
		solve();
	}
}

B - Array Decrements

主要看ai 于bi之间的差和ai 与0之间的差大小，第二种情况不能大于第一种情况。

#include "bits/stdc++.h"
using namespace std;
#pragma GCC optimize(2)

#define int long long 
#define endl '\n'
#define IOS ios::sync_with_stdio(0),cin.tie(0);
#define all(x) x.begin(),x.end()
#define pi pair<int,int> 
#define vi vector<int>

void solve()
{
	int n;
	cin>>n;
	
	vi a(n);
	vi b(n);
	
	for (int i=0;i<n;i++){
		cin>>a[i];
	}
	for (int i=0;i<n;i++){
		cin>>b[i];
	}
	
	int x=0,y=1e9;
	for (int i=0;i<n;i++){
		if(b[i]==0){
			x=max(x,a[i]);
		}
		else {
			x=max(x,a[i]-b[i]);
			y=min(a[i]-b[i],y);
			
			
		}
	}
	
	
	if(x<=y){
		cout<<"YES"<<endl;
	}
	else {
		cout<<"no"<<endl;
	}
}
signed main()
{
	IOS
	int t;
	cin>>t;
	while(t--){
		solve();
	}
}

C - Restoring the Duration of Tasks

可以理解为多个区段的首尾判断，枚举一次，每次更新下一区段的开始位置即可。

#include "bits/stdc++.h"
using namespace std;
#pragma GCC optimize(2)

#define int long long 
#define endl '\n'
#define IOS ios::sync_with_stdio(0),cin.tie(0);
#define all(x) x.begin(),x.end()
#define pi pair<int,int> 
#define vi vector<int>

void solve()
{
	int n;
	cin>>n;
	
	vi a(n);
	vi b(n);
	
	for (int i=0;i<n;i++){
		cin>>a[i];
	}
	for (int i=0;i<n;i++){
		cin>>b[i];
	}
	
	vi c;
	int last,begin;
	for (int i=0;i<n;i++){
		if(i==0){
			c.push_back(b[i]-a[i]);
			last=b[i];
		}else {
			if(a[i]<=last){
				begin=last;
			}
			else {
				begin=a[i];
			}
			
			c.push_back(b[i]-begin);
			last=b[i];
			
			
		}
	}
	
	
	for (int i=0;i<n;i++){
		cout<<c[i]<<" ";
	}
	cout<<endl;

}
signed main()
{
	IOS
	int t;
	cin>>t;
	while(t--){
		solve();
	}
}

D - Black and White Stripe

可以通过前缀和记录w的数量，来查找k的区间中，w的最小数量。

#include "bits/stdc++.h"
using namespace std;
#pragma GCC optimize(2)

#define int long long 
#define endl '\n'
#define IOS ios::sync_with_stdio(0),cin.tie(0);
#define all(x) x.begin(),x.end()
#define pi pair<int,int> 
#define vi vector<int>

void solve()
{
	int n,k;
	cin>>n>>k;
	
	string  s;
	cin>>s;
	vi a(n+1);
	for (int i=0;i<n;i++){
		a[i+1]=a[i]+(s[i]=='W');
	}
	int ans=k;
	for (int i=0;i<=n-k;i++){
		ans=min(ans,a[i+k]-a[i]);
	}

	cout<<ans<<endl;

}
signed main()
{
	IOS
	int t;
	cin>>t;
	while(t--){
		solve();
	}
}

E - Price Maximization

本来以为是找一对尽量和可以被k整除的数，后来改为先记录每一个物品除 k 的商，每个数取余数

在使用双指针从头尾扫刚好大于等于k的数，更新总和。

#include "bits/stdc++.h"
using namespace std;


#define int long long 
#define endl '\n'
#define IOS ios::sync_with_stdio(0),cin.tie(0);
#define all(x) x.begin(),x.end()
#define pi pair<int,int> 
#define vi vector<int>


void solve()
{
	int n,k;
	cin>>n>>k;
	
	vi a(n);
	int sum=0;

	for (int i=0;i<n;i++){
		cin>>a[i];
		sum+=a[i]/k;
		a[i]%=k;
		
	}
	
    sort(a.begin(),a.end(),greater());
	
	for (int l=0,r=n-1;l<r;l++,r--){
		while(a[l]+a[r]<k && l<r) r--;
		if(l==r){
			break;
		}
		sum++;
	}
	
	cout<<sum<<endl;
	

	

}
signed main()
{
	IOS
	int t;
	cin>>t;
	while(t--){
		solve();
	}
}