此篇属于比赛题解集合(CF && AcWing Race)链接

比赛地址
https://codeforces.com/contest/1822

考试过了 abcd

后来补了efg

思路先咕咕咕，先考试期中，传个代码

A

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>

using namespace std;
int T;

const int N = 200;
int a[N];
int b[N];
vector<int>tmp;

void solve()
{
  int n,m;
  cin >> n >> m;
  tmp.clear();
  for(int i = 1;i <= n;i ++)
  {
    cin >> a[i];a[i] += i-1;
    if(a[i] <= m) tmp.push_back(i);
  }
  int resid = 0;
  int res = 0;
  for(int i = 1;i<= n;i ++) cin >> b[i];
  if(tmp.size())
  {
    for(auto t:tmp)
    { 
      if(res < b[t])
      {
        resid = t;
        res = b[t];
      }
    }
    cout << resid << endl;
  }
  else cout << -1 << endl;

}

int main()
{
  ios::sync_with_stdio(false);
  cin >> T;
  while(T--)
      solve();
}

B

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>
#define int long long

const int INF = 0x3f3f3f3f3f3f3f3f;
using namespace std;
const int N = 2e5 + 10;
int T;
int n;
int a[N];
int cnt = 0;
int maxxx;
void solve2()
{
    sort(a + 1, a + n + 1);
        if (a[1] < 0 && a[2] < 0)
        {
            maxxx = max(a[1] * a[2], maxxx);
        }
        if (a[n] > 0 && a[n - 1] > 0)
        {
            maxxx = max(a[n] * a[n - 1], maxxx);
        }
        if (cnt)
        {
            maxxx = max(maxxx,0ll);
        }
    maxxx = max(maxxx, a[1] * a[2]);
    maxxx = max(maxxx, a[n] * a[n - 1]);

}
void solve()
{
     cin >> n;
         maxxx= -INF;
     cnt = 0;

        for (int i = 1; i <= n; i ++ ) 
        {
            cin >> a[i];
            if (!a[i]) cnt ++ ;
        }
        if (cnt == n || cnt == n - 1)
        {
            cout << 0 << endl;
            return;
        }
        solve2();
        cout << maxxx << endl;
}

signed main()
{
  ios::sync_with_stdio(false);
  cin >> T;
  while(T--)
      solve();
}

C

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<cmath>
#define int long long

using namespace std;
int T;

int a;
void solve()
{
    cin >> a;
        a = a - 3;
        cout << 9 * a + a * (a - 1) + 17 << endl;
}

signed main()
{
  ios::sync_with_stdio(false);
  cin >> T;
  while(T--)
      solve();
}

D

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>

using namespace std;

const int N = 2e5 + 10;
int T;
int n;
int a[N];


void solve()
{
   cin >> n;
   if(n == 1)
   {
    cout << 1 << endl;
    return;
   }
   if(n%2)
   {
    cout << -1 << endl;
    return;
   }
   a[0] = n;a[n/2]=n/2;
   int x = 1;
   for(int i = 1;i < n/2;i ++)
   {
      if(x)
      {
      a[i] = n - i;
      a[n-i] = i;
      }
      else
     {
        a[i] = i;
        a[n-i] = n - i;
      }
      x ^= 1;
   }
   for(int i = 0;i < n;i ++) cout << a[i] << ' ';
   cout << endl;

}

int main()
{
  ios::sync_with_stdio(false);
  cin >> T;
  while(T--)
      solve();
}

E

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>
#define int long long
#define pb push_back

using namespace std;
const int N = 2e5 + 10;
int T;
int cnt[30];
int single_cnt[30];
bool used[30];
vector<int> id;
string x;

void init()
{
  id.clear();
  memset(used,false,sizeof used);
  memset(cnt,0,sizeof cnt);
  memset(single_cnt,0,sizeof single_cnt);
}

void pr()
{
  for(int i = 0;i < 26;i ++)
  cout << cnt[i] << ' ';
  cout << endl;
}

void solve()
{
    init();

    int n;cin >> n;
    cin >> x;
    if(n % 2) 
    {
      cout << -1 << endl;
      return;
    }

    for(int i = 0;i < n/2;i ++)
    {
      single_cnt[x[i]-'a'] ++;
      single_cnt[x[n - i - 1]-'a']++;
      if(x[i] == x[n - i - 1])
      {
        int ch = x[i] - 'a';
        if(!used[ch])
        id.pb(ch),used[ch] = true;
        cnt[ch]++;
      }
    }

    //pr();

    for(int i = 0;i < 26;i ++)
    if(single_cnt[i] > n/2) 
    {
      cout << -1 << endl;
      return;
    }

    int sum = 0;int res = 0;
    //pr();
    //cout << "id ";
    //for(int t : id)
    //cout << t << ' ';
    //cout << endl;
    for(int t : id) sum += cnt[t]; int odd = sum%2;
    for(int t : id) 
    {
      if(cnt[t] > sum/2)
      {
        res += sum/2;
        res += cnt[t] - sum/2;
        cout << res << endl;
        return;
      }
    }
     res += sum/2 + odd;
     cout << res << endl;


}

signed main()
{
  ios::sync_with_stdio(false);
  cin >> T;
  while(T--)
      solve();
}

F

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>
#include<queue>

using namespace std;

using LL = long long;
int T;


void solve()
{
   int n,k,c;
   cin >> n >> k >> c;
   vector<vector<int> >g(n);
   for(int i = 0;i < n - 1;i ++)
   {
    int a,b;cin >> a >> b;a--,b--;
    g[a].push_back(b);
    g[b].push_back(a);
   }

   auto bfs = [&](int st)
   {
      vector<int> d(n,-1);
      queue<int> q;
      d[st] = 0;
      q.push(st);
      while(!q.empty())
      {
        int t = q.front();q.pop();
        for(auto j : g[t])
        {
          if(d[j] == -1)
          {
            d[j] = d[t] + 1;
            q.push(j);
          }
        }
      }
      return d;
   };

   auto d1 = bfs(0);
   int p = max_element(d1.begin(),d1.end()) - d1.begin();
   auto d2 = bfs(p);
   int q = max_element(d2.begin(),d2.end()) - d2.begin();
   auto d3 = bfs(q);

  LL res = 0;
  for(int i = 0;i < n;i ++)
  res = max(res,1LL * k * max(d2[i],d3[i]) - 1ll * c * d1[i]);
  cout << res << endl;

}

int main()
{
  ios::sync_with_stdio(false);
  cin >> T;
  while(T--)
      solve();
}

G

思路代码来自cup神

#include<iostream>
#include<cstring>
#include<vector>
#include<map>
using namespace std;
using LL = long long;

vector<int> go_fac(int n){ 
    vector<int> f;
    for(int i = 1; i * i <= n; i++){
        if (n % i == 0){
            f.push_back(i);
            if (i * i != n) f.push_back(n / i);
        }
    }
    return f;
}


int main(){

    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);

    const int uplimit = 1e9;
    const int S = 1e6;

    auto C3 = [&](int x){
        return 1LL * x * (x - 1) * (x - 2);
    };

    int T;
    cin >> T;
    while(T--){
        int n;
        cin >> n;
        map<int, int> mp;
        for(int i = 1; i <= n; i++){
            int x;
            cin >> x;
            mp[x] += 1;
        }
        LL ans = 0;
        for(auto &[x, y] : mp){
            ans += C3(y);
            if (x >= S){
                for(int j = 2; 1LL * j * x <= uplimit; j++){
                    if (x % j == 0 && mp.count(x * j) && mp.count(x / j)){
                        ans += 1LL * y * mp[x * j] * mp[x / j];
                    }
                }
            }
            else{
                auto f = go_fac(x);
                sort(f.begin(), f.end());
                for(auto u : f){
                    if (u == 1) continue;
                    if (1LL * x * u > uplimit) break;
                    if (mp.count(x / u) && mp.count(x * u)){
                        ans += 1LL * y * mp[x / u] * mp[x * u];
                    }
                }
            }
        }
        cout << ans << '\n';
    }

}