Educational Codeforces Round 31
A. Book Reading
暴力
view code
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast,no-stack-protector")
#include<bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define endl "\n"
#define LL long long int
#define vi vector<int>
#define vl vector<LL>
#define all(V) V.begin(),V.end()
#define sci(x) scanf("%d",&x)
#define scl(x) scanf("%I64d",&x)
#define pii pair<int,int>
#define pll pair<LL,LL>
#ifndef ONLINE_JUDGE
#define cout cerr
#endif
#define cmax(a,b) ((a) = (a) > (b) ? (a) : (b))
#define cmin(a,b) ((a) = (a) < (b) ? (a) : (b))
#define debug(x) cerr << #x << " = " << x << endl
function<void(void)> ____ = [](){ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);};
template <typename T> vector<T>& operator << (vector<T> &__container, T x){ __container.push_back(x); return __container; }
template <typename T> ostream& operator << (ostream &out, vector<T> &__container){ for(T _ : __container) out << _ << ' '; return out; }
const int MAXN = 2e5+7;
void solve(){
int n, t;
sci(n); sci(t);
vi A(n);
for(int &x : A) sci(x);
int tt = 0;
for(int i = 0; i < n; i++){
tt += 86400 - A[i];
if(tt>=t){
cout << i + 1 << endl;
return;
}
}
cout << n << endl;
}
int main(){
#ifndef ONLINE_JUDGE
freopen("Local.in","r",stdin);
freopen("ans.out","w",stdout);
#endif
solve();
return 0;
}
B. Japanese Crosswords Strike Back
确定唯一，必须是每中间插一个\(0\)
view code
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast,no-stack-protector")
#include<bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define endl "\n"
#define LL long long int
#define vi vector<int>
#define vl vector<LL>
#define all(V) V.begin(),V.end()
#define sci(x) scanf("%d",&x)
#define scl(x) scanf("%I64d",&x)
#define pii pair<int,int>
#define pll pair<LL,LL>
#ifndef ONLINE_JUDGE
#define cout cerr
#endif
#define cmax(a,b) ((a) = (a) > (b) ? (a) : (b))
#define cmin(a,b) ((a) = (a) < (b) ? (a) : (b))
#define debug(x) cerr << #x << " = " << x << endl
function<void(void)> ____ = [](){ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);};
template <typename T> vector<T>& operator << (vector<T> &__container, T x){ __container.push_back(x); return __container; }
template <typename T> ostream& operator << (ostream &out, vector<T> &__container){ for(T _ : __container) out << _ << ' '; return out; }
const int MAXN = 2e5+7;
void solve(){
int n, x;
sci(n); sci(x);
vi A(n);
for(int &x : A) sci(x);
if(accumulate(all(A),0)+n-1==x) cout << "YES" << endl;
else cout << "NO" << endl;
}
int main(){
#ifndef ONLINE_JUDGE
freopen("Local.in","r",stdin);
freopen("ans.out","w",stdout);
#endif
solve();
return 0;
}
C. Bertown Subway
找出所有置换环，把最大的两个连起来即可
view code
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast,no-stack-protector")
#include<bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define endl "\n"
#define LL long long int
#define vi vector<int>
#define vl vector<LL>
#define all(V) V.begin(),V.end()
#define sci(x) scanf("%d",&x)
#define scl(x) scanf("%I64d",&x)
#define pii pair<int,int>
#define pll pair<LL,LL>
#ifndef ONLINE_JUDGE
#define cout cerr
#endif
#define cmax(a,b) ((a) = (a) > (b) ? (a) : (b))
#define cmin(a,b) ((a) = (a) < (b) ? (a) : (b))
#define debug(x) cerr << #x << " = " << x << endl
function<void(void)> ____ = [](){ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);};
template <typename T> vector<T>& operator << (vector<T> &__container, T x){ __container.push_back(x); return __container; }
template <typename T> ostream& operator << (ostream &out, vector<T> &__container){ for(T _ : __container) out << _ << ' '; return out; }
const int MAXN = 2e5+7;
void solve(){
int n; sci(n);
vi A(n); for(int &x : A) sci(x);
vi loop;
vi vis(n,0);
LL ret = 0;
for(int i = 0; i < n; i++){
if(vis[i]) continue;
int u = i, sz = 0;
while(!vis[u]){
sz++;
vis[u] = true;
u = A[u] - 1;
}
loop << sz;
ret += 1ll * sz * sz;
}
sort(all(loop),greater<int>());
if(loop.size()==1) cout << ret << endl;
else ret += (loop[0]+loop[1]+0ll) * (loop[0]+loop[1]) - 1ll * loop[0] * loop[0] - 1ll * loop[1] * loop[1], cout << ret << endl;
}
int main(){
#ifndef ONLINE_JUDGE
freopen("Local.in","r",stdin);
freopen("ans.out","w",stdout);
#endif
solve();
return 0;
}
D. Boxes And Balls
霍夫曼编码，如果是偶数的话加一个\(0\)，然后每次取最小的三个合并
view code
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast,no-stack-protector")
#include<bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define endl "\n"
#define LL long long int
#define vi vector<int>
#define vl vector<LL>
#define all(V) V.begin(),V.end()
#define sci(x) scanf("%d",&x)
#define scl(x) scanf("%I64d",&x)
#define pii pair<int,int>
#define pll pair<LL,LL>
#ifndef ONLINE_JUDGE
#define cout cerr
#endif
#define cmax(a,b) ((a) = (a) > (b) ? (a) : (b))
#define cmin(a,b) ((a) = (a) < (b) ? (a) : (b))
#define debug(x) cerr << #x << " = " << x << endl
function<void(void)> ____ = [](){ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);};
template <typename T> vector<T>& operator << (vector<T> &__container, T x){ __container.push_back(x); return __container; }
template <typename T> ostream& operator << (ostream &out, vector<T> &__container){ for(T _ : __container) out << _ << ' '; return out; }
const int MAXN = 2e5+7;
void solve(){
int n; sci(n);
vi A(n); for(int &x : A) sci(x);
priority_queue<LL,vl,greater<LL> > que;
for(int &x : A) que.push(x);
LL ret = 0;
if(!(que.size()&1)) que.push(0);
while(que.size()!=1){
LL x = que.top(); que.pop();
LL y = que.top(); que.pop();
LL z = que.top(); que.pop();
ret += x + y + z;
que.push(x+y+z);
}
cout << ret << endl;
}
int main(){
#ifndef ONLINE_JUDGE
freopen("Local.in","r",stdin);
freopen("ans.out","w",stdout);
#endif
solve();
return 0;
}
E. Binary Matrix
看似卡空间
实则卡时间
暴力来做的话把每个所有位置并查集一下就好了
由于空间只有\(16MB\)，那就一行一行来处理就行了
记一下上一行有哪些位置是联通的
view code
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast,no-stack-protector")
#include<bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define endl "\n"
#define LL long long int
#define vi vector<int>
#define vl vector<LL>
#define all(V) V.begin(),V.end()
#define sci(x) scanf("%d",&x)
#define scl(x) scanf("%I64d",&x)
#define pii pair<int,int>
#define pll pair<LL,LL>
#ifndef ONLINE_JUDGE
#define cout cerr
#endif
#define cmax(a,b) ((a) = (a) > (b) ? (a) : (b))
#define cmin(a,b) ((a) = (a) < (b) ? (a) : (b))
#define debug(x) cerr << #x << " = " << x << endl
function<void(void)> ____ = [](){ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);};
template <typename T> vector<T>& operator << (vector<T> &__container, T x){ __container.push_back(x); return __container; }
template <typename T> ostream& operator << (ostream &out, vector<T> &__container){ for(T _ : __container) out << _ << ' '; return out; }
const int MAXN = (1<<15) + 7;
int f[MAXN];
int exc(char c){
if(isdigit(c)) return c - '0';
else return c - 'A' + 10;
}
int n, m;
bool last[MAXN], now[MAXN];
char str[MAXN];
int findx(int x){ return x == f[x] ? x : f[x] = findx(f[x]); }
void solve(){
int ret = 0;
sci(n); sci(m);
for(int i = 0; i < m * 2; i++) f[i] = i;
while(n--){
scanf("%s",str);
for(int i = 0; i < m / 4; i++){
int x = exc(str[i]);
for(int j = 0; j < 4; j++) now[i*4+3-j] = (x>>j&1);
}
int cont = 0;
for(int i = 0; i < m; i++) if(now[i]) cont++;
for(int i = 0; i < m; i++){
if(!now[i]) continue;
if(i!=0 and now[i-1] and findx(i)!=findx(i-1)) f[findx(i)] = findx(i-1), cont--;
if(last[i] and findx(i)!=findx(i+m)) f[findx(i+m)] = findx(i), cont--;
}
for(int i = 0; i < m; i++) findx(i);
for(int i = 0; i < m; i++) f[i+m] = f[i] + m, f[i] = i;
ret += cont;
for(int i = 0; i < m; i++) last[i] = now[i];
}
cout << ret << endl;
}
int main(){
#ifndef ONLINE_JUDGE
freopen("Local.in","r",stdin);
freopen("ans.out","w",stdout);
#endif
solve();
return 0;
}
F. Anti-Palindromize
费用流，源点向每个字符连边，容量为字符出现次数，费用为\(0\)
每个位置向汇点连边，容量为\(1\)，费用为\(0\)
接下来对称的位置对每个字符公用一个点，用于限流，字符点向新增的这个点连容量\(1\)，费用\(0\)的点，然后再这个点向对称的两个位置分别连容量为\(1\)，费用为对应费用的边
view code
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast,no-stack-protector")
#include<bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define endl "\n"
#define LL long long int
#define vi vector<int>
#define vl vector<LL>
#define all(V) V.begin(),V.end()
#define sci(x) scanf("%d",&x)
#define scl(x) scanf("%I64d",&x)
#define pii pair<int,int>
#define pll pair<LL,LL>
#ifndef ONLINE_JUDGE
#define cout cerr
#endif
#define cmax(a,b) ((a) = (a) > (b) ? (a) : (b))
#define cmin(a,b) ((a) = (a) < (b) ? (a) : (b))
#define debug(x) cerr << #x << " = " << x << endl
function<void(void)> ____ = [](){ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);};
template <typename T> vector<T>& operator << (vector<T> &__container, T x){ __container.push_back(x); return __container; }
template <typename T> ostream& operator << (ostream &out, vector<T> &__container){ for(T _ : __container) out << _ << ' '; return out; }
const int MAXN = 2e3+7;
int pre[MAXN], dist[MAXN], flow[MAXN], preid[MAXN];
bool vis[MAXN];
#define S 0
#define T MAXN - 1
struct EDGE{
int to,cap,fee,rev;
EDGE(){}
EDGE(int _to, int _cap, int _fee, int _rev){
to = _to; cap = _cap;
fee = _fee; rev = _rev;
}
};
vector<EDGE> G[MAXN];
void ADDEDGE(int u, int v, int cap, int fee){
G[u].emplace_back(EDGE(v,cap,fee,(int)G[v].size()));
G[v].emplace_back(EDGE(u,0,-fee,(int)G[u].size()-1));
}
bool spfa(){
memset(dist,0x3f,sizeof(dist));
dist[S] = 0;
flow[S] = INF;
memset(vis,0,sizeof(vis));
queue<int> que;
que.push(S);
while(!que.empty()){
int u = que.front();
que.pop();
vis[u] = 0;
for(int i = 0; i < (int)G[u].size(); i++){
auto e = G[u][i];
if(!e.cap or dist[e.to]<=dist[u]+e.fee) continue;
dist[e.to] = dist[u] + e.fee;
flow[e.to] = min(e.cap,flow[u]);
pre[e.to] = u; preid[e.to] = i;
if(!vis[e.to]){
vis[e.to] = 1;
que.push(e.to);
}
}
}
return dist[T]!=INF;
}
int mcmf(){
int cost = 0;
while(spfa()){
int u = T;
cost += dist[T] * flow[T];
while(u!=S){
int p = pre[u], id = preid[u];
G[p][id].cap -= flow[T];
G[u][G[p][id].rev].cap += flow[T];
u = pre[u];
}
}
return cost;
}
char s[MAXN];
int n, w[MAXN], cnt[26];
void solve(){
sci(n);
scanf("%s",s+1);
for(int i = 1; i <= n; i++) sci(w[i]);
for(int i = 1; i <= n; i++) cnt[s[i]-'a']++;
for(int i = 1; i <= 26; i++) ADDEDGE(S,i,cnt[i-1],0);
for(int i = 1; i <= n; i++) ADDEDGE(26+i,T,1,0);
int tot = 26 + n;
for(int i = 1; i <= n/2; i++){
for(int j = 0; j < 26; j++){
tot++;
ADDEDGE(j+1,tot,1,0);
ADDEDGE(tot,26+i,1,j==s[i]-'a'?-w[i]:0);
ADDEDGE(tot,26+n+1-i,1,j==s[n+1-i]-'a'?-w[n+1-i]:0);
}
}
cout << -mcmf() << endl;
}
int main(){
#ifndef ONLINE_JUDGE
freopen("Local.in","r",stdin);
freopen("ans.out","w",stdout);
#endif
solve();
return 0;
}
