D-游游的k-好数组_牛客周赛 Round 6 (nowcoder.com)（关键--a[1]=a[k+1]）

#include<iostream>
#include<algorithm>
using namespace std;
const int N=100005;
int a[N]; 
typedef pair<int,int>PII;
PII b[N];
void solve(){int n,k,x;cin>>n>>k>>x;for(int i=1;i<=n;i++){cin>>a[i];b[i%k].first=0;b[i%k].second=0;}for(int i=1;i<=n;i++){b[i%k].first=max(a[i],b[i%k].first);b[i%k].second++;}for(int i=1;i<=n;i++){x-=b[i%k].first-a[i];}if(x<0){cout<<-1<<endl;return;}sort(b,b+k);int ma=-1;for(int i=k-1;i>=0;i--){if(b[i].second!=0&&ma==-1)ma=b[i].first;if(b[i].second<=x&&b[i].second>0){ma=max(ma,b[i].first+x/b[i].second);}}cout<<ma<<endl;
}
int main(){int t;cin>>t;while(t--){solve();}
} 

Problem - E2 - Codeforces

#include<iostream>
#include<algorithm>
#include<map>
#include<string>
#include<cstring>
using namespace std;
const int N=200005;
int a[N]; 
typedef pair<int,int>PII;
bool vis[N];
int cnt[27];
char s[N],t[N];
int n,k;
void dfs(int u){vis[u]=true;cnt[s[u]-'a']--;cnt[t[u]-'a']++;if(u-k>=1&&!vis[u-k])dfs(u-k);if(u-(k+1)>=1&&!vis[u-(k+1)])dfs(u-(k+1));if(u+k<=n&&!vis[u+k])dfs(u+k);if(u+k+1<=n&&!vis[u+k+1])dfs(u+k+1);
}
void solve(){cin>>n>>k;cin>> (s+1) >> (t+1) ;memset(vis,0,sizeof(vis));for(int i=1;i<=n;i++){if(!vis[i]){memset(cnt,0,sizeof(cnt));dfs(i);for(int i=0;i<26;i++){if(cnt[i]!=0){cout<<"NO"<<endl;return;}}}}cout<<"YES"<<endl;
}
int main(){int t;cin>>t;while(t--){solve();}
}