Codeforces Beta Round #49 (Div. 2)
http://codeforces.com/contest/53
A
1 #include<bits/stdc++.h> 2 using namespace std; 3 #define lson l,mid,rt<<1 4 #define rson mid+1,r,rt<<1|1 5 #define sqr(x) ((x)*(x)) 6 #define pb push_back 7 #define eb emplace_back 8 #define maxn 1000005 9 #define rep(k,i,j) for(int k=i;k<j;k++) 10 typedef long long ll; 11 typedef unsigned long long ull; 12 13 string s[105]; 14 15 int main(){ 16 #ifndef ONLINE_JUDGE 17 freopen("input.txt","r",stdin); 18 #endif 19 std::ios::sync_with_stdio(false); 20 string str; 21 cin>>str; 22 int n; 23 cin>>n; 24 for(int i=1;i<=n;i++){ 25 cin>>s[i]; 26 } 27 string ans=str; 28 int flag=0; 29 for(int i=1;i<=n;i++){ 30 if(s[i].find(str)==0){ 31 if(!flag) ans=s[i],flag=1; 32 else ans=min(ans,s[i]); 33 } 34 } 35 cout<<ans<<endl; 36 }
B
二分+枚举
1 #include<bits/stdc++.h> 2 using namespace std; 3 #define lson l,mid,rt<<1 4 #define rson mid+1,r,rt<<1|1 5 #define sqr(x) ((x)*(x)) 6 #define pb push_back 7 #define eb emplace_back 8 #define maxn 1000005 9 #define rep(k,i,j) for(int k=i;k<j;k++) 10 #define eps 1e-8 11 typedef long long ll; 12 typedef unsigned long long ull; 13 14 15 ///w/h>=0.8&&w/h<=1.25 16 17 ll num[35]; 18 ll h,w; 19 20 int sgn(double x){ 21 if(x<0) return -1; 22 if(x<eps) return 0; 23 return 1; 24 } 25 vector<double>tmp; 26 27 bool Check1(ll mid,ll h){ 28 double zhi=(mid*1.0)/(h*1.0); 29 if(sgn(zhi-0.8)>=0&&sgn(1.25-zhi)>=0) return true; 30 return false; 31 } 32 33 bool Check2(ll h,ll mid){ 34 double zhi=(mid*1.0)/(h*1.0); 35 if(sgn(zhi-0.8)>=0&&sgn(1.25-zhi)>=0) return true; 36 return false; 37 } 38 39 int main(){ 40 #ifndef ONLINE_JUDGE 41 // freopen("input.txt","r",stdin); 42 #endif 43 std::ios::sync_with_stdio(false); 44 cin>>h>>w; 45 num[0]=1; 46 ll l,r,mid; 47 ll ans=0; 48 ll ansh,answ; 49 for(int i=1;i<=30;i++) num[i]=num[i-1]*2; 50 for(int i=0;i<=30;i++){ 51 if(h>=num[i]){ 52 l=ll(ceil(num[i]*0.8)); 53 54 if(ll(num[i]*1.25)<=w) r=num[i]*1.25; 55 else r=w; 56 // if(h==5&&w==5) cout<<l<<" "<<r<<endl; 57 if(l>r) continue; 58 while(l<=r){ 59 mid=l+r>>1; 60 if(Check1(mid,num[i])) l=mid+1; 61 else r=mid-1; 62 } 63 if(ans<=r*num[i]){ 64 ans=r*num[i]; 65 ansh=num[i],answ=r; 66 } 67 } 68 } 69 for(int i=0;i<=30;i++){ 70 if(w>=num[i]){ 71 /* l=ll(ceil(num[i]/0.8)); 72 if(ll(num[i]/1.25)<=w) r=num[i]*1.25; 73 else r=h;*/ 74 l=ceil(num[i]*1.0/1.25); 75 r=min(h,ll(num[i]*1.0/0.8)); 76 // cout<<l<<" "<<r<<endl; 77 // if(h==5&&w==5) cout<<l<<" "<<r<<endl; 78 if(l>r) continue; 79 while(l<=r){ 80 81 mid=l+r>>1;//cout<<mid<<endl; 82 if(Check2(num[i],mid)) l=mid+1; 83 else r=mid-1; 84 } 85 if(ans<=r*num[i]){ 86 ans=r*num[i]; 87 answ=num[i],ansh=r; 88 } 89 } 90 } 91 if(ansh<answ){ 92 if(answ<=h) swap(ansh,answ); 93 } 94 cout<<ansh<<" "<<answ<<endl; 95 }
C
找规律
1 #include<bits/stdc++.h> 2 using namespace std; 3 #define lson l,mid,rt<<1 4 #define rson mid+1,r,rt<<1|1 5 #define sqr(x) ((x)*(x)) 6 #define pb push_back 7 #define eb emplace_back 8 #define maxn 1000005 9 #define rep(k,i,j) for(int k=i;k<j;k++) 10 typedef long long ll; 11 typedef unsigned long long ull; 12 13 14 15 int main(){ 16 #ifndef ONLINE_JUDGE 17 // freopen("input.txt","r",stdin); 18 #endif 19 std::ios::sync_with_stdio(false); 20 int n; 21 cin>>n; 22 int L=1,R=n; 23 for(int i=1;i<=n;i++){ 24 if(i%2){ 25 cout<<L++<<" "; 26 } 27 else{ 28 cout<<R--<<" "; 29 } 30 } 31 32 }
D
模拟
1 #include<bits/stdc++.h> 2 using namespace std; 3 #define lson l,mid,rt<<1 4 #define rson mid+1,r,rt<<1|1 5 #define sqr(x) ((x)*(x)) 6 #define pb push_back 7 #define eb emplace_back 8 #define maxn 1000005 9 #define rep(k,i,j) for(int k=i;k<j;k++) 10 typedef long long ll; 11 typedef unsigned long long ull; 12 13 int a[305],b[305]; 14 vector<pair<int,int> >ve; 15 16 int main(){ 17 #ifndef ONLINE_JUDGE 18 // freopen("input.txt","r",stdin); 19 #endif 20 std::ios::sync_with_stdio(false); 21 int n; 22 cin>>n; 23 for(int i=1;i<=n;i++) cin>>a[i]; 24 for(int i=1;i<=n;i++) cin>>b[i]; 25 int j; 26 for(int i=1;i<=n;i++){ 27 if(a[i]!=b[i]){ 28 for(j=i+1;j<=n;j++){ 29 if(a[i]==b[j]){ 30 break; 31 } 32 } 33 for(;j>i;j--){ 34 ve.pb(make_pair(j-1,j)); 35 swap(b[j],b[j-1]); 36 } 37 } 38 } 39 cout<<ve.size()<<endl; 40 for(int i=0;i<ve.size();i++){ 41 cout<<ve[i].first<<" "<<ve[i].second<<endl; 42 } 43 }
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
1 #include<bits/stdc++.h> 2 using namespace std; 3 #define lson l,mid,rt<<1 4 #define rson mid+1,r,rt<<1|1 5 #define sqr(x) ((x)*(x)) 6 #define pb push_back 7 #define eb emplace_back 8 #define maxn 1000005 9 #define rep(k,i,j) for(int k=i;k<j;k++) 10 typedef long long ll; 11 typedef unsigned long long ull; 12 13 int n,m,k; 14 int g[25][25]; 15 int dp[1055][1055]; 16 int ans; 17 18 int main(){ 19 #ifndef ONLINE_JUDGE 20 // freopen("input.txt","r",stdin); 21 #endif 22 std::ios::sync_with_stdio(false); 23 cin>>n>>m>>k; 24 int u,v,x; 25 rep(i,0,m){ 26 cin>>u>>v; 27 u--,v--; 28 x=(1<<u)|(1<<v); 29 g[u][v]=g[v][u]=1; 30 dp[x][x]=1; 31 } 32 rep(i,0,1<<n){ 33 rep(j,0,1<<n){ 34 if(i&j==j&&dp[i][j]){ 35 rep(k,0,n){ 36 rep(w,0,n){ 37 if (g[k][w]&&(i&(1<<k))&&(~i&(1<<w))&&(!(((j&(~(1<<k)))|(1<<w))>>(w+1)))){ 38 dp[i|(1<<w)][(j&(~(1<<k)))|((1<<w))]+=dp[i][j]; 39 } 40 } 41 } 42 } 43 } 44 } 45 int nn=(1<<n)-1; 46 rep(i,0,1<<n){ 47 if(__builtin_popcount(i)==k){ 48 ans+=dp[nn][i]; 49 } 50 } 51 cout<<ans<<endl; 52 }