Educational Codeforces Round 151 (Rated for Div. 2)(A-B)

news2024/12/29 9:37:31

打完涨了20分……
算法选修课就学会了dfs……如果有期末复习的这种劲头，其他算法估计早就学会了（

A Forbidden Integer

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这个还WA了三发……

signed main(){
	IOS;
	int n,k,x;
	bool f=1;
	cf{
		cin>>n>>k>>x;
		if(k==1)cout<<"NO"<<endl;
		else{
			if(x==1){
				if(n%2==0){
					cout<<"YES"<<endl;
					cout<<n/2<<endl;
					fer(i,0,n/2)cout<<"2"<<" ";
					cout<<endl;
				}else{
					if(k==2)cout<<"NO"<<endl;
					else {
						cout<<"YES"<<endl;
						cout<<n/2<<endl;
						fer(i,0,n/2-1)cout<<"2"<<" ";
						cout<<3<<endl;
					}
					
				}
			}else {
				cout<<"YES"<<endl;
				cout<<n<<endl;
				fer(i,0,n)cout<<"1"<<" ";
				cout<<endl;
			}
		}
	}
	return 0;
}

B Come Together

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signed main(){
	IOS;
	int xa,ya,xb,yb,xc,yc;
	int res;
	cf{
		cin>>xa>>ya>>xb>>yb>>xc>>yc;
		xb-=xa;yb-=ya;
		xc-=xa;yc-=ya;
		res=1;
		if((xb>0&&xc>0)||(xb<0&&xc<0))res+=min(abs(xb),abs(xc));
		if((yb>0&&yc>0)||(yb<0&&yc<0))res+=min(abs(yb),abs(yc));
		cout<<res<<endl;
	}
	return 0;
	
}

C Strong Password

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好好读题……
dfs回溯+剪枝+优化也没过……tle on test 7，不过有人dfs过了，不知有无被hack

string s,l,r;
int m;
bool f;
string res="";
pair<int,int> check(int starti,int startj){
	int finali=0,finalj=0;
	int i=starti+1,j=startj+1;
	while(i<s.size()&&j<res.size()){
		if(s[i]==res[j]){
			finali=i,finalj=j;
			j++;
		}
		i++;
	}
	if(j!=res.size())f=1;
	return make_pair(finali,finalj);
}
void dfs(int t,int starti,int startj){
	if(t==m){
		//cout<<res<<endl;
		check(starti,startj);
		return;
	}
	fer(i,l[t]-'0',r[t]-'0'+1){
		char tmp=i+'0';
		res+=tmp;
		pair<int,int> pr;
		pr=check(starti,startj);
		if(f){
			res="";
			return;
		}
		else {
			dfs(t+1,pr.first,pr.second);
			if(f){
				res="";return;
			}
			res.pop_back();
		}
	}
}
signed main(){
	IOS;
	cf{
		cin>>s;
		cin>>m;
		cin>>l>>r;
		f=0;
		dfs(0,-1,-1);
		if(f)cout<<"YES"<<endl;
		else cout<<"NO"<<endl;
	}
	return 0;
	
}