Codeforces Round #541 (Div. 2)

Codeforces Round #541 (Div. 2)

http://codeforces.com/contest/1131

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;

 int main(){
     #ifndef ONLINE_JUDGE
       //  freopen("input.txt","r",stdin);
     #endif
     std::ios::sync_with_stdio(false);
     ll w1,h1,w2,h2;
     cin>>w1>>h1>>w2>>h2;
     ll tmp1=(w2+)*(h2+);//上面的
     ll tmp2=(w1+)*(h1+);
     ll tmp3=w1*h1+w2*h2;
     ll ans=tmp1+tmp2-tmp3-*(w2+);
     cout<<ans<<endl;
 }

B

 #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;
     ll a,b,x,y;
     x=,y=;
     ll ans=;
     for(int i=;i<=n;i++){
         cin>>a>>b;
         ans+=max(0LL,min(a,b)-max(x,y)+(x!=y));
         x=a,y=b;
     }
     cout<<ans<<endl;
 }

C

sort排序，然后从小到大依次左右各添一个向中间添加。。。在比赛的时候第一感觉这就是正解，但是不会证明为什么。。。

 #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[];
 int ans[];

 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];
     sort(a+,a+n+);
     int L=,R=n;
     int i=;
     while(L<=R){
         if(i%)
             ans[L++]=a[i];
         else
             ans[R--]=a[i];
         i++;
     }
     for(int i=;i<=n;i++) cout<<ans[i]<<" ";
 }

D

用并查集把相同的点连在一起，然后剩下的点用拓扑排序即可

 #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 2005
 #define rep(k,i,j) for(int k=i;k<j;k++)
 typedef long long ll;
 typedef unsigned long long ull;

 int n,m;
 char str[][];

 int fa[maxn];
 int d[maxn];
 int vis[maxn];
 int ans[maxn];
 vector<int>ve[maxn];

 int Find(int x){
     int r=x,y;
     while(x!=fa[x]){
         x=fa[x];
     }
     while(r!=x){
         y=fa[r];
         fa[r]=x;
         r=y;
     }
     return x;
 }

 void join(int x,int y){
      int xx=Find(x);
      int yy=Find(y);
      fa[xx]=yy;
 }

 void add(int x,int y){
     int xx=Find(x);
     int yy=Find(y);
     if(xx!=yy){
         d[xx]++;
         ve[yy].pb(xx);
     }
     else{
         cout<<"NO"<<endl;
         exit();
     }
 }

 void topsort(){
     queue<pair<int,int> >Q;
     rep(i,,n+m+){
         int xx=Find(i);
         if(!d[xx]&&!vis[xx]){
             vis[xx]=;
             Q.push(make_pair(xx,));
         }
     }
     pair<int,int>pp;
     while(!Q.empty()){
         pp=Q.front();
         Q.pop();
         int pos=pp.first;
         int v=pp.second;
         ans[pos]=v;
         rep(i,,ve[pos].size()){
             int w=ve[pos][i];
             d[w]--;
             if(!d[w]){
                 Q.push(make_pair(w,v+));
             }
         }
     }
     rep(i,,n+m+){
         if(d[i]){
             cout<<"NO"<<endl;
             exit();
         }
     }
 }

 int main(){
     #ifndef ONLINE_JUDGE
         freopen("input.txt","r",stdin);
     #endif
     std::ios::sync_with_stdio(false);
     cin>>n>>m;
     rep(i,,n+m+) fa[i]=i;
     rep(i,,n+) cin>>(str[i]+);
     rep(i,,n+){
         rep(j,,m+){
             if(str[i][j]=='='){
                 join(Find(i),Find(j+n));
             }
         }
     }
     rep(i,,n+){
         rep(j,,m+){
             if(str[i][j]=='>'){
                 add(i,n+j);
             }
             else if(str[i][j]=='<'){
                 add(n+j,i);
             }
         }
     }
     topsort();
     cout<<"YES"<<endl;
     rep(i,,n+) cout<<ans[Find(i)]<<" ";
     cout<<endl;
     rep(i,,m+) cout<<ans[Find(i+n)]<<" ";
 }

E

类似模拟的方法

找出字符串的连续前缀，连续后缀和中间最长连续子串

 #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 ans=;
 string s[];

 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>>s[i];
     }
     for(int c=;c<;c++){
         int l=,r=,all=;
         for(int i=n-;i>=;i--){
             int cnt=,pf=,sf=,tt=;
             while(pf<s[i].length()&&s[i][pf]=='a'+c) ++pf;
             while(sf<s[i].length()&&s[i][s[i].length()--sf]=='a'+c) ++sf;
             for(int j=;j<s[i].length();j++){
                 if(s[i][j]=='a'+c){
                     cnt=max(cnt,++tt);
                 }
                 else{
                     tt=;
                 }
             }
             if(all){
                 ans=max(ans,(cnt+)*(l+)-);
                 l=(pf+)*(l+)-;
                 r=(sf+)*(r+)-;
                 if(pf!=s[i].length()){
                     all=;
                 }
             }
             else{
                 if(cnt){
                     ans=max(ans,l+r+);
                 }
             }
         }
     }
     cout<<ans<<endl;
 }

F

比赛的时候犯傻了，一直在想建图，然后找度为1的点，然后深搜的错误性。。没想出来。后来才知道了错误性

正解应该是：并查集，合并就完事了

 #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;

 vector<int>ve[];

 int fa[];

 int Find(int x){
     int r=x,y;
     while(x!=fa[x]){
         x=fa[x];
     }
     while(r!=x){
         y=fa[r];
         fa[r]=x;
         r=y;
     }
     return x;
 }

 void join(int x,int y){
     int xx=Find(x);
     int yy=Find(y);
     if(ve[xx].size()>ve[yy].size()){
         swap(xx,yy);
     }
     rep(i,,ve[xx].size()){
         ve[yy].pb(ve[xx][i]);
         fa[ve[xx][i]]=yy;
     }
 }

 int main(){
     #ifndef ONLINE_JUDGE
         freopen("input.txt","r",stdin);
     #endif
     std::ios::sync_with_stdio(false);
     int n;
     cin>>n;
     rep(i,,n+) fa[i]=i,ve[i].pb(i);
     int u,v;
     rep(i,,n){
         cin>>u>>v;
         join(u,v);
     }
     int pos=Find();
     rep(i,,ve[pos].size()){
         cout<<ve[pos][i]<<" ";
     }

 }