Educational Codeforces Round 85 (Rated for Div. 2)

A

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

#define int long long
const int N = 1005;

int t,n,p[N],c[N];

signed main() {
    ios::sync_with_stdio(false);
    cin>>t;
    while(t--) {
        cin>>n;
        for(int i=1;i<=n;i++) cin>>p[i]>>c[i];
        int fg=1;
        for(int i=1;i<=n;i++) if(p[i]<p[i-1] || c[i]<c[i-1]) fg=0;
        for(int i=1;i<=n;i++) if(p[i]-p[i-1]<c[i]-c[i-1]) fg=0;
        if(fg) puts("YES");
        else puts("NO");
    }
}

B

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

#define int long long
const int N = 100005;

int t,n,x,a[N];

signed main() {
    ios::sync_with_stdio(false);
    cin>>t;
    while(t--) {
        cin>>n>>x;
        for(int i=1;i<=n;i++)cin>>a[i];
        sort(a+1,a+n+1);
        reverse(a+1,a+n+1);
        int s=0,c=0;
        for(int i=1;i<=n;i++) {
            s+=a[i];
            c++;
            if(s<c*x) {
                c--;
                break;
            }
        }
        cout<<c<<endl;
    }
}

C

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

#define int long long
const int N = 300005;

int t,n,a[N],b[N];

signed main() {
    ios::sync_with_stdio(false);
    cin>>t;
    while(t--) {
        cin>>n;
        for(int i=1;i<=n;i++) cin>>a[i]>>b[i];
        int sum=0;
        a[0]=a[n];b[0]=b[n];
        for(int i=1;i<=n;i++) sum+=max(a[i]-b[i-1],0ll);
        int ans=1e18;
        for(int i=1;i<=n;i++) ans=min(ans,sum+a[i]-max(a[i]-b[i-1],0ll));
        cout<<ans<<endl;
    }
}

D
很容易发现按照 1 2 1 3 1 4 2 3 2 4 3 4 1 这样构造即可

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

#define int long long
int t,n,l,r;

signed main() {
    ios::sync_with_stdio(false);
    cin>>t;
    while(t--) {
        cin>>n>>l>>r;
        int i=1;
        int x=0;
        while(l-x>2*(n-i) && i<=n) {
            x+=2*(n-i);
            i++;
        }
        int j=(l-x+1)/2+i;
        int len=r-l+1;
        if(l%2==0) {
            cout<<j<<" ", --len;
            ++j;
            if(j>n) j=(++i)+1;
        }
        while(len>0) {
            if(i>=n) i=1,j=1;
            cout<<i<<" ";
            if(len>1) cout<<j<<" ";
            ++j;
            if(j>n) j=(++i)+1;
            if(i>=n) i=1,j=1;
            len-=2;
        }
        cout<<endl;
    }

}