Codeforces Beta Round #49 (Div. 2)

Codeforces Beta Round #49 (Div. 2)

http://codeforces.com/contest/53

A

 #include<bits/stdc++.h>
 using namespace std;
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define sqr(x) ((x)*(x))
 #define pb push_back
 #define eb emplace_back
 #define maxn 1000005
 #define rep(k,i,j) for(int k=i;k<j;k++)
 typedef long long ll;
 typedef unsigned long long ull;

 string s[];

 int main(){
     #ifndef ONLINE_JUDGE
         freopen("input.txt","r",stdin);
     #endif
     std::ios::sync_with_stdio(false);
     string str;
     cin>>str;
     int n;
     cin>>n;
     for(int i=;i<=n;i++){
         cin>>s[i];
     }
     string ans=str;
     int flag=;
     for(int i=;i<=n;i++){
         if(s[i].find(str)==){
             if(!flag) ans=s[i],flag=;
             else ans=min(ans,s[i]);
         }
     }
     cout<<ans<<endl;
 }

B

二分+枚举

 #include<bits/stdc++.h>
 using namespace std;
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define sqr(x) ((x)*(x))
 #define pb push_back
 #define eb emplace_back
 #define maxn 1000005
 #define rep(k,i,j) for(int k=i;k<j;k++)
 #define eps 1e-8
 typedef long long ll;
 typedef unsigned long long ull;

 ///w/h>=0.8&&w/h<=1.25

 ll num[];
 ll h,w;

 int sgn(double x){
     if(x<) return -;
     if(x<eps) return ;
     return ;
 }
 vector<double>tmp;

 bool Check1(ll mid,ll h){
     double zhi=(mid*1.0)/(h*1.0);
     if(sgn(zhi-0.8)>=&&sgn(1.25-zhi)>=) return true;
     return false;
 }

 bool Check2(ll h,ll mid){
     double zhi=(mid*1.0)/(h*1.0);
     if(sgn(zhi-0.8)>=&&sgn(1.25-zhi)>=) return true;
     return false;
 }

 int main(){
     #ifndef ONLINE_JUDGE
      //   freopen("input.txt","r",stdin);
     #endif
     std::ios::sync_with_stdio(false);
     cin>>h>>w;
     num[]=;
     ll l,r,mid;
     ll ans=;
     ll ansh,answ;
     for(int i=;i<=;i++) num[i]=num[i-]*;
     for(int i=;i<=;i++){
         if(h>=num[i]){
             l=ll(ceil(num[i]*0.8));

             if(ll(num[i]*1.25)<=w) r=num[i]*1.25;
             else r=w;
          //   if(h==5&&w==5) cout<<l<<" "<<r<<endl;
             if(l>r) continue;
             while(l<=r){
                 mid=l+r>>;
                 if(Check1(mid,num[i])) l=mid+;
                 else r=mid-;
             }
             if(ans<=r*num[i]){
                 ans=r*num[i];
                 ansh=num[i],answ=r;
             }
         }
     }
     for(int i=;i<=;i++){
         if(w>=num[i]){
            /* l=ll(ceil(num[i]/0.8));
             if(ll(num[i]/1.25)<=w) r=num[i]*1.25;
             else r=h;*/
             l=ceil(num[i]*1.0/1.25);
             r=min(h,ll(num[i]*1.0/0.8));
           //  cout<<l<<" "<<r<<endl;
            // if(h==5&&w==5) cout<<l<<" "<<r<<endl;
             if(l>r) continue;
             while(l<=r){

                 mid=l+r>>;//cout<<mid<<endl;
                 if(Check2(num[i],mid)) l=mid+;
                 else r=mid-;
             }
             if(ans<=r*num[i]){
                 ans=r*num[i];
                 answ=num[i],ansh=r;
             }
         }
     }
     if(ansh<answ){
         if(answ<=h) swap(ansh,answ);
     }
     cout<<ansh<<" "<<answ<<endl;
 }

C

找规律

 #include<bits/stdc++.h>
 using namespace std;
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define sqr(x) ((x)*(x))
 #define pb push_back
 #define eb emplace_back
 #define maxn 1000005
 #define rep(k,i,j) for(int k=i;k<j;k++)
 typedef long long ll;
 typedef unsigned long long ull;

 int main(){
     #ifndef ONLINE_JUDGE
      //   freopen("input.txt","r",stdin);
     #endif
     std::ios::sync_with_stdio(false);
     int n;
     cin>>n;
     int L=,R=n;
     for(int i=;i<=n;i++){
         if(i%){
             cout<<L++<<" ";
         }
         else{
             cout<<R--<<" ";
         }
     }

 }

D

模拟

 #include<bits/stdc++.h>
 using namespace std;
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define sqr(x) ((x)*(x))
 #define pb push_back
 #define eb emplace_back
 #define maxn 1000005
 #define rep(k,i,j) for(int k=i;k<j;k++)
 typedef long long ll;
 typedef unsigned long long ull;

 int a[],b[];
 vector<pair<int,int> >ve;

 int main(){
     #ifndef ONLINE_JUDGE
      //   freopen("input.txt","r",stdin);
     #endif
     std::ios::sync_with_stdio(false);
     int n;
     cin>>n;
     for(int i=;i<=n;i++) cin>>a[i];
     for(int i=;i<=n;i++) cin>>b[i];
     int j;
     for(int i=;i<=n;i++){
         if(a[i]!=b[i]){
             for(j=i+;j<=n;j++){
                 if(a[i]==b[j]){
                     break;
                 }
             }
             for(;j>i;j--){
                 ve.pb(make_pair(j-,j));
                 swap(b[j],b[j-]);
             }
         }
     }
     cout<<ve.size()<<endl;
     for(int i=;i<ve.size();i++){
         cout<<ve[i].first<<" "<<ve[i].second<<endl;
     }
 }

E

状压DP

这题思路很奇妙，有些细节还没理解清楚

参考博客：https://www.luogu.org/problemnew/solution/CF53E

 #include<bits/stdc++.h>
 using namespace std;
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define sqr(x) ((x)*(x))
 #define pb push_back
 #define eb emplace_back
 #define maxn 1000005
 #define rep(k,i,j) for(int k=i;k<j;k++)
 typedef long long ll;
 typedef unsigned long long ull;

 int n,m,k;
 int g[][];
 int dp[][];
 int ans;

 int main(){
     #ifndef ONLINE_JUDGE
      //   freopen("input.txt","r",stdin);
     #endif
     std::ios::sync_with_stdio(false);
     cin>>n>>m>>k;
     int u,v,x;
     rep(i,,m){
         cin>>u>>v;
         u--,v--;
         x=(<<u)|(<<v);
         g[u][v]=g[v][u]=;
         dp[x][x]=;
     }
     rep(i,,<<n){
         rep(j,,<<n){
             if(i&j==j&&dp[i][j]){
                 rep(k,,n){
                     rep(w,,n){
                         if (g[k][w]&&(i&(<<k))&&(~i&(<<w))&&(!(((j&(~(<<k)))|(<<w))>>(w+)))){
                             dp[i|(<<w)][(j&(~(<<k)))|((<<w))]+=dp[i][j];
                         }
                     }
                 }
             }
         }
     }
     int nn=(<<n)-;
     rep(i,,<<n){
         if(__builtin_popcount(i)==k){
             ans+=dp[nn][i];
         }
     }
     cout<<ans<<endl;
 }