Educational Codeforces Round 100 (Rated for Div. 2)

Educational Codeforces Round 100 (Rated for Div. 2)

• A

#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize(2)
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
void io(){ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);}

int t,a,b,c;

int main()
{
    io();
    cin>>t;
    
    while(t--){
        cin>>a>>b>>c;
        int sum=a+b+c;
        int x=(7*sum)/9;
        if(9*x==7*sum){
            int minn=min(a,min(b,c));
            if(x/7>minn) cout<<"NO
";
            else cout<<"YES
";
        }
        else cout<<"NO
";
    }
    return 0;
}

• B
  • 设奇数下标存1，偶数下标存原数，(sum_{i=1}^n{|a[i]-b[i]|}=A)，同理，相反为(B),设奇数下标存0，偶数下标存原数，(sum_{i=1}^n{|a[i]-b[i]|}=A')，同理相反为(B')

  • [ A' ge A \ B' ge B \ sum-B'=A' \ If A' > frac{sum}{2} \ Then B' leq frac{sum}{2}\So Ble frac{sum}{2} ]

#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize(2)
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
void io() { ios::sync_with_stdio(false); cin.tie(0); cout.tie(0); }

int t, n;
int a[100], b[100];

int solve(int x,int y)
{
    for(int i=1;i<=sqrt(x);++i){
        if(x%i==0){
            if(abs(y-i)<=y/2) return i;
            if(abs(y-x/i)<=y/2) return x/i;
        }
    }
}


int main()
{
    io();
    cin >> t;
    while (t--) {
        cin >> n;
        ll sum = 0;
        int maxx = 0;
        for (int i = 1; i <= n; ++i) {
            cin >> a[i];
            sum += a[i] * 1ll;
        }
        ll ts=0;
        for(int i=1;i<=n;++i){
            if(i%2){
                b[i]=1;
            }else b[i]=a[i];
            ts+=1ll*abs(a[i]-b[i]);
        }
        if(ts*2ll<=sum) goto ww;
        // for(int i=1;i<=n;++i){
        //     if(a[i]==1||a[i]==2) b[i]=1;
        //     else b[i]=a[pos];
        // }
        ts=0;
        for(int i=1;i<=n;++i){
            if(i%2==0){
                b[i]=1;
            }else b[i]=a[i];
            ts+=1ll*abs(a[i]-b[i]);
        }
        ww:for (int i = 1; i <= n; ++i) cout << b[i] << " ";
        cout << "
";
    }
    return 0;
}

• C

#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize(2)
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
void io() { ios::sync_with_stdio(false); cin.tie(0); cout.tie(0); }

const ll maxn = 1e5 + 10;
ll T, n;
ll t[maxn], x[maxn];
ll flag[10];


int main()
{
    io();
    cin >> T;
    while (T--) {
        cin >> n;
        memset(flag, 0, sizeof(flag));
        for (ll i = 1; i <= n; ++i) cin >> t[i] >> x[i];
        t[n + 1] = 1e18 + 10;
        ll x0 = 0, nextt = abs(x[1]) + t[1];
        ll np = 0; // nowPlace
        ll ep = x[1];
        flag[0] = x[1] < x[0] ? 1 : 0; // 1往-走，0往+走
        ll ans = 0;
        for (ll i = 1; i <= n; ++i) {
            if (t[i] >= nextt) {
                nextt = t[i] + abs(ep - x[i]);
                flag[0] = x[i] < ep ? 1 : 0;
                np = ep;
                ep = x[i];
            }
            ll tmp = t[i + 1] - t[i];
            ll tep = flag[0] ? np - tmp : np + tmp;// tempEndPlace
            if ((x[i] >= np && x[i] <= tep) || (x[i] >= tep && x[i] <= np)) {
                if (flag[0]) {
                    if (x[i] >= ep) ans++;
                }
                if (!flag[0]) {
                    if (x[i] <= ep) ans++;
                }
            }
            flag[0] ? np -= tmp : np += tmp;
        }
        cout << ans << "
";
    }
    return 0;
}