ABC412题解A to F

A

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#include <stdio.h>
int n, ans;
int main() {
	scanf("%d", &n);
	for (int i = 1, a, b; i <= n; i++) {
		scanf("%d %d", &a, &b);
		if (a < b) ans++;
	}
	printf("%d", ans);
	return 0;
}

B

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#include <stdio.h>
#include <string.h>
#include <stdbool.h>
char s[101], t[101];
bool vis[101];
int main() {
	scanf("%s %s", s, t);
	for (int i = 0; i < strlen(t); i++) vis[t[i] - 'A'] = 1;
	for (int i = 1; i < strlen(s); i++)
		if (s[i] >= 'A' && s[i] <= 'Z')
			if (!vis[s[i - 1] - 'A']) {
				printf("No");
				return 0;
			}
	printf("Yes");
	return 0;
}

C

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#include <stdio.h>
#include <string.h>
#include <stdbool.h>
char s[101], t[101];
bool vis[101];
int main() {
	scanf("%s %s", s, t);
	for (int i = 0; i < strlen(t); i++) vis[t[i] - 'A'] = 1;
	for (int i = 1; i < strlen(s); i++)
		if (s[i] >= 'A' && s[i] <= 'Z')
			if (!vis[s[i - 1] - 'A']) {
				printf("No");
				return 0;
			}
	printf("Yes");
	return 0;
}

D

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#include <stdio.h>
#include <set>
int n, m, d[10], ans = 1e9;
bool flag[10][10];
void dfs(int i, int u, int v, int cnt, int ecnt)
{
	if (ecnt > n || ecnt + ((n * (n - 1) >> 1) - i) < n)
		return;
	if (v == n + 1)
		v = 1 + ++u;
	if (u == n)
	{
		for (int i = 1; i <= n; ++i)
			if (d[i] != 2)
				return;
		if (cnt < ans)
			ans = cnt;
		return;
	}
	++d[u];
	++d[v];
	dfs(i + 1, u, v + 1, cnt + 1 - flag[u][v], ecnt + 1);
	--d[u];
	--d[v];
	dfs(i + 1, u, v + 1, cnt + flag[u][v], ecnt);
}
int main()
{
	scanf("%d%d", &n, &m);
	for (int i = 1, u, v; i <= m; ++i)
	{
		scanf("%d%d", &u, &v);
		if (u > v)
			u ^= v ^= u ^= v;
		flag[u][v] = true;
	}
	dfs(0, 1, 2, 0, 0);
	printf("%d\n", ans);
	return 0;
}

E

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

using ll =long long;


const ll NM=1e7;
bool P[NM+1];

void init(){
    for(int i=0;i<=NM;i++)P[i]=1;
    P[0]=P[1]=0;
    for(int i=0;i<=NM;i++){
        if(P[i])for(int j=i*2;j<=NM;j+=i)P[j]=0;
    }
    return;
}


int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    init();
    ll L,R;
    cin>>L>>R;
  if(L==R){
    cout<<1<<"\n";
    return 0;
  }
    L++;
  
    vector<ll> C(R-L+1,0);
    for(int i=0;i<=NM;i++){
        if(P[i]){
            ll f=((L-1)/i*i)+i;
            while(f<=R){
                ll id=f-L;
                f+=i;
                if(C[id]==-1){
                    continue;
                }
                else if(C[id]==0)C[id]=i;
                else C[id]=-1;
            }
        }
    }
    ll an=1;
    for(int i=0;i<=R-L;i++){
        ll d=i+L;
        if(C[i]==0){
            an++;
        }
        else if(C[i]>0){
            while(d%C[i]==0)d/=C[i];
            if(d==1){
                an++;
            }

        }
    }
    cout<<an<<"\n";
}

F

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#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double db;
#define rep(x,l,r) for(int x=l;x<=r;x++)
#define per(x,r,l) for(int x=r;x>=l;x--)
#define pb push_back
#define mp make_pair
#define all(v) v.begin(),v.end()

const int MOD=998244353,INF=1e9;
const ll LNF=1e18;
int power(int a,int k,int mod=MOD) {
    a%=mod,k%=mod-1; if(k<0) k+=mod-1;
    int res=1; while(k) {
        if(k&1) res=1ll*res*a%mod;
        a=1ll*a*a%mod; k>>=1;
    } return res;
}
void add(int &x,int y) {x=(x+y>=MOD?x+y-MOD:x+y);}
void sub(int &x,int y) {x=(x>=y?x-y:x-y+MOD);}
int gcd(int x,int y) {return y?gcd(y,x%y):x;}
void chkmax(int &x,int y) {x<y?x=y:0;}
void chkmin(int &x,int y) {x>y?x=y:0;}

const int N=300300;

int n,m,c;
int a[N],b;

int f[N];

int main() {
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    cin>>n>>c;
    rep(i,1,n) cin>>a[i];
    m=0; rep(i,1,n) m+=a[i];
    b=++a[c];
    sort(a+1,a+n+1);
    rep(i,1,n) if(a[i]==b) c=i;
    int tot=-1,sum=1;
    per(i,n,1) {
        tot+=a[i];
        f[i]=1ll*sum*m%MOD*power(tot,-1)%MOD;
        sum=(sum+1ll*f[i]*a[i]%MOD*power(m,-1))%MOD;
        // cout<<' '<<i<<' '<<tot<<' '<<sum<<'\n';
    }
    cout<<f[c]<<'\n';
    // rep(i,1,n) cout<<a[i]<<' '; cout<<'\t'<<'\t'<<c<<'\n';
    // rep(i,1,n) cout<<f[i]<<' '; cout<<'\n';
    return 0;
}