A. Three Arrays
列舉每個$a_i$，雙指標出$b$和$c$的範圍，對於$b$中每個預先雙指標出$c$的範圍，那麼對於每個$b$，在對應$c$的區間加$1$，在$a$處區間求和即可。
樹狀陣列維護，時間複雜度$O(n\log n)$。
#include<stdio.h>
#include<iostream>
#include<string.h>
#include<string>
#include<ctype.h>
#include<math.h>
#include<set>
#include<map>
#include<vector>
#include<queue>
#include<bitset>
#include<algorithm>
#include<time.h>
using namespace std;
void fre() { }
#define MS(x, y) memset(x, y, sizeof(x))
#define ls o<<1
#define rs o<<1|1
typedef long long LL;
typedef unsigned long long UL;
typedef unsigned int UI;
template <class T1, class T2>inline void gmax(T1 &a, T2 b) { if (b > a)a = b; }
template <class T1, class T2>inline void gmin(T1 &a, T2 b) { if (b < a)a = b; }
const int N = 5e5 + 10, M = 0, Z = 1e9 + 7, inf = 0x3f3f3f3f;
template <class T1, class T2>inline void gadd(T1 &a, T2 b) { a = (a + b) % Z; }
int casenum, casei;
int n;
int d;
int na, nb, nc;
int a[N], b[N], c[N];
int lc[N], rc[N];
LL suml[N], sumr[N];
struct BIT
{
LL v[N];
LL vx[N];
void init()
{
memset(v, 0, (n + 2) << 3);
memset(vx, 0, (n + 2) << 3);
}
void add(int x, LL V)
{
LL VX = V * (x - 1);
for (; x <= n; x += x & -x)
{
v[x] += V;
vx[x] += VX;
}
}
LL check(int x)
{
LL ret = 0;
for(int i = x; i ; i -= i & -i)
{
ret += v[i] * x;
ret -= vx[i];
}
return ret;
}
}bit;
void ADD(int p, int val)
{
int l = lc[p];
int r = rc[p];
bit.add(l, val);
bit.add(r + 1, -val);
}
LL CHECK(int l, int r)
{
return bit.check(r) - bit.check(l - 1);
}
int main()
{
while(~scanf("%d", &d))
{
bit.init();
scanf("%d%d%d", &na, &nb, &nc);
n = nc + 10;
for(int i = 1; i <= na; ++i)scanf("%d", &a[i]);
for(int i = 1; i <= nb; ++i)scanf("%d", &b[i]);
for(int i = 1; i <= nc; ++i)scanf("%d", &c[i]);
int l = 1, r = 0;
for(int i = 1; i <= nb; ++i)
{
while(r < nc && c[r + 1] <= b[i] + d)++r;
while(l <= nc && c[l] < b[i] - d)++l;
lc[i] = l;
rc[i] = r;
}
for(int i = 1; i <= nb; ++i)
{
sumr[i] = sumr[i - 1] + rc[i];
suml[i] = suml[i - 1] + lc[i];
}
l = 1, r = 0;
int L = 1, R = 0;
LL ans = 0;
int ll = 1, rr = 0;
for(int i = 1; i <= na; ++i)
{
while(rr < nc && c[rr + 1] <= a[i] + d)++rr;
while(ll <= nc && c[ll] < a[i] - d)++ll;
while(R < nb && b[R + 1] <= a[i] + d)
{
ADD(++R, 1);
}
while(L <= nb && b[L] < a[i] - d)
{
ADD(L++, -1);
}
if(rr >= ll)ans += CHECK(ll, rr);
/*
while(rr < nc && c[rr + 1] <= a[i] + d)++rr;
while(ll <= nc && c[ll] < a[i] - d)++ll;
while(R < nb && b[R + 1] <= a[i] + d)++R;
while(L <= nb && b[L] < a[i] - d)++L;
while(r < nb && rc[r + 1] <= a[i] + d)++r;
while(l <= nb && lc[l] < a[i] - d)++l;
if(L > R)continue;
if(ll > rr)continue;
if(r >= l)
{
ans += sumr[r] - sumr[L - 1];
ans += (LL)(R - r) * rr;
ans -= suml[R] - suml[l - 1];
ans -= (LL)((l - 1) - (L - 1)) * ll;
ans += (R - L + 1);
}
else
{
printf("LRlr llrr: %d %d %d %d %d %d %d\n", i, L, R, l, r, ll, rr);
ans += (LL)(R - L + 1) * (rr - ll + 1);
}
printf("%lld\n", sumr[r] - sumr[L - 1]);
printf("%lld\n", (LL)(R - r) * (a[i] + d));
printf("%lld\n", suml[R] - suml[l - 1]);
printf("%lld\n", (LL)((l - 1) - (L - 1)) * (a[i] - d));
printf("%d %d %d %d\n", L, R, l, r);
printf("%d %lld\n", i, ans);
*/
}
printf("%lld\n", ans);
}
return 0;
}
/*
【trick&&吐槽】
1 3 3 3
1 2 3
1 2 3
1 2 3
1 6 6 6
1 1 2 2 3 3
2 2 3 3 4 4
3 3 4 4 5 5
【題意】
【分析】
【時間複雜度&&優化】
*/
B. Expected Shopping
高精度。
C. Cover the Paths
貪心，按照LCA的深度從深到淺選擇。
#include<cstdio>
#include<algorithm>
using namespace std;
const int N=100010,M=262150;
int Case,cas,n,m,q,i,op,x,y,z;
int g[N],v[N<<1],nxt[N<<1],ed;
int size[N],son[N],f[N],d[N],st[N],top[N],dfn;
int val[M];
int ans,choose[N];
struct E{int x,y,z;}e[N];
inline bool cmp(const E&a,const E&b){return d[a.z]<d[b.z];}
inline void addedge(int x,int y){v[++ed]=y;nxt[ed]=g[x];g[x]=ed;}
void dfs(int x){
size[x]=1;
for(int i=g[x];i;i=nxt[i])if(v[i]!=f[x]){
f[v[i]]=x,d[v[i]]=d[x]+1;
dfs(v[i]),size[x]+=size[v[i]];
if(size[v[i]]>size[son[x]])son[x]=v[i];
}
}
void dfs2(int x,int y){
st[x]=++dfn;top[x]=y;
if(son[x])dfs2(son[x],y);
for(int i=g[x];i;i=nxt[i])if(v[i]!=son[x]&&v[i]!=f[x])dfs2(v[i],v[i]);
}
void build(int x,int a,int b){
val[x]=0;
if(a==b)return;
int mid=(a+b)>>1;
build(x<<1,a,mid),build(x<<1|1,mid+1,b);
}
void change(int x,int a,int b,int c){
val[x]++;
if(a==b)return;
int mid=(a+b)>>1;
if(c<=mid)change(x<<1,a,mid,c);
else change(x<<1|1,mid+1,b,c);
}
int ask(int x,int a,int b,int c,int d){
if(c<=a&&b<=d)return val[x];
int mid=(a+b)>>1,t=0;
if(c<=mid)t=ask(x<<1,a,mid,c,d);
if(d>mid)t+=ask(x<<1|1,mid+1,b,c,d);
return t;
}
inline int lca(int x,int y){
for(;top[x]!=top[y];x=f[top[x]])if(d[top[x]]<d[top[y]])swap(x,y);
return d[x]<d[y]?x:y;
}
inline int chain(int x,int y){
int t=0;
for(;top[x]!=top[y];x=f[top[x]]){
if(d[top[x]]<d[top[y]])swap(x,y);
t+=ask(1,1,n,st[top[x]],st[x]);
}
if(d[x]<d[y])swap(x,y);
t+=ask(1,1,n,st[y],st[x]);
return t;
}
inline void gao(int x,int y,int z){
if(chain(x,y))return;
choose[++ans]=z;
change(1,1,n,st[z]);
}
int main(){
scanf("%d",&n);
for(i=1;i<n;i++){
scanf("%d%d",&x,&y);
addedge(x,y),addedge(y,x);
}
dfs(1);
dfs2(1,1);
build(1,1,n);
scanf("%d",&m);
for(i=1;i<=m;i++){
scanf("%d%d",&x,&y);
e[i].x=x,e[i].y=y;
e[i].z=lca(x,y);
}
sort(e+1,e+m+1,cmp);
for(i=m;i;i--)gao(e[i].x,e[i].y,e[i].z);
printf("%d\n",ans);
for(i=1;i<=ans;i++)printf("%d ",choose[i]);
}
D. Elevator
若$t_i<t_j$且$a_i\leq a_j$，那麼$j$可以順手帶走$i$，故可以剔除這些$i$使得$a$嚴格遞減。
設$f_i$表示前$i$個人分組的最短時間，則$f_i=\min(\max(f_j,t_i)+2a_{j+1})$，其中$0\leq j<i$，且$f_j<t_{i+1}$，不然不能將$i$和$i+1$分開。
討論$\max$的來源，Treap維護即可。
時間複雜度$O(n\log n)$。
#include<cstdio>
#include<cstdlib>
#include<algorithm>
using namespace std;
typedef long long ll;
const int N=200010;
const ll inf=1LL<<60;
int n,m,i;
ll f[N];
struct P{
ll t,a;
}a[N],q[N];
inline bool cmp(const P&a,const P&b){
return a.t<b.t;
}
struct node{
ll val,dp,mi;
int p;
node*l,*r;
node(){
val=0;
dp=mi=inf;
p=0;
l=r=NULL;
}
void up(){
mi=min(dp,min(l->mi,r->mi));
}
}*blank=new(node),*root[2],pool[N*2],*cur;
inline void Rotatel(node*&x){node*y=x->r;x->r=y->l;x->up();y->l=x;y->up();x=y;}
inline void Rotater(node*&x){node*y=x->l;x->l=y->r;x->up();y->r=x;y->up();x=y;}
void Ins(node*&x,ll p,ll v){
if(x==blank){
x=new(node);
x->val=p;
x->dp=x->mi=v;
x->l=x->r=blank;
x->p=rand();
return;
}
x->mi=min(x->mi,v);
if(p==x->val){
x->dp=min(x->dp,v);
return;
}
if(p<x->val){
Ins(x->l,p,v);
if(x->l->p>x->p)Rotater(x);
}else{
Ins(x->r,p,v);
if(x->r->p>x->p)Rotatel(x);
}
}
ll Ask(node*x,ll a,ll b,ll c,ll d){
if(x==blank)return inf;
if(c<=a&&b<=d)return x->mi;
ll t=c<=x->val&&x->val<=d?x->dp:inf;
if(c<x->val)t=min(t,Ask(x->l,a,x->val-1,c,d));
if(d>x->val)t=min(t,Ask(x->r,x->val+1,b,c,d));
return t;
}
inline void ins(int x){
if(f[x]>=inf)return;
Ins(root[0],f[x],q[x+1].a);
Ins(root[1],f[x],f[x]+q[x+1].a);
}
int main(){
blank->l=blank->r=blank;
while(~scanf("%d",&n)){
for(i=1;i<=n;i++)scanf("%lld%lld",&a[i].t,&a[i].a),a[i].a*=2;
sort(a+1,a+n+1,cmp);
m=0;
for(i=1;i<=n;i++){
while(m&&q[m].a<=a[i].a)m--;
q[++m]=a[i];
}
q[m+1].t=inf;
root[0]=root[1]=blank;
ins(0);
for(i=1;i<=m;i++){
f[i]=min(Ask(root[0],0,inf,0,q[i].t)+q[i].t,Ask(root[1],0,inf,q[i].t,q[i+1].t-1));
ins(i);
}
printf("%lld\n",f[m]);
}
}
E. Code-Cola Plants
對於集合$a$，要滿足除$a$以外每個點恰有一條入邊，對於集合$b$，要滿足除$b$以外每個點恰有一條出邊。
建立二分圖，左邊$2n-2$個點，分別表示每個點需要入邊和出邊，右邊$m$個點，表示原圖一條邊，那麼右邊每個點可以供給左邊至多兩個點。
Hopcroft求最大匹配即可通過。
時間複雜度$O(n\sqrt{n})$。
#include<cstdio>
#include<cstring>
#include<queue>
#include<algorithm>
using namespace std;
const int N= 1e6 + 10;
int n1, n2;
vector<int> g[N];
int mx[N], my[N];
int que[N*5];
int head,tail;
int dx[N], dy[N];
bool vis[N];
bool find(int u){
for(int i = 0; i < g[u].size(); i ++)
if(! vis[g[u][i]] && dy[g[u][i]] == dx[u] + 1){
vis[g[u][i]] = true;
if(! my[g[u][i]] || find(my[g[u][i]])){
mx[u] = g[u][i];
my[g[u][i]] = u;
return true;
}
}
return false;
}
int matching()
{
memset(mx, 0, (n1 + 5) << 2);
memset(my, 0, (n2 + 5) << 2);
int ans = 0;
while(true){
bool flag = false;
head=1,tail=0;
memset(dx, 0, (n1 + 5) << 2);
memset(dy, 0, (n2 + 5) << 2);
for(int i = 1; i <= n1; i ++)
if(! mx[i])que[++tail]=i;
while(head<=tail){
int u = que[head++];
for(int i = 0; i < g[u].size(); i ++)
if(! dy[g[u][i]]){
dy[g[u][i]] = dx[u] + 1;
if(my[g[u][i]]){
dx[my[g[u][i]]] = dy[g[u][i]] + 1;
que[++tail]=my[g[u][i]];
}
else flag = true;
}
}
if(! flag) break;
memset(vis, 0, max(n1,n2)+5);
for(int i = 1; i <= n1; i ++)
if(! mx[i] && find(i)) ans ++;
}
return ans;
}
int n, m, a, b;
int main(){
while(~ scanf("%d%d%d%d", &n, &m, &a, &b)){
n1 = m; n2 = 2 * n ;
for(int i = 1; i <= m; i ++){
int x, y;
scanf("%d%d", &x, &y);
g[i].clear();
if(a != y) g[i].push_back(y);
if(b != x)g[i].push_back(x + n);
}
int ans = matching();
if(ans == 2 * n - 2){
puts("YES");
for(int i = 1; i <= n; i ++){
if(i != a) printf("%d ", my[i]);
}puts("");
for(int i = n + 1; i <= n + n ; i ++){
if(i != b + n) printf("%d ", my[i]);
}puts("");
}
else puts("NO");
}
}
/*
4 7 1 4
1 2
1 2
1 4
2 3
2 3
3 4
3 4
4 3 1 2
1 2
2 4
4 3
5 8 3 1
3 2
5 2
3 4
4 5
4 1
2 1
3 5
3 1
*/
F. GCD
即保留至少$m-k$個數使得$\gcd$最大，因為$k\leq\frac{n}{2}$，故每個數屬於最優解的概率至少為$\frac{1}{2}$。
多次隨機選擇一個數，認為它必選，那麼將其分解質因數，高維字首和統計每個約數是多少個數的約數即可。
在$10^{18}$內約數個數最大值不超過$200000$，故可以通過。
#include<cstdio>
#include<algorithm>
#include<cstdlib>
using namespace std;
typedef long long ll;
const int C=2730,S=5;
const int N=222222;
int n,m,i,j,k;
int len[N];
ll pr[N][30][2];
ll pool[N];
ll ans;
int cnt;
ll gcd(ll a, ll b) {return b ? gcd(b, a % b) : a;}
ll mul(ll a, ll b, ll n){return (a * b - (ll)(a / (long double) n * b + 1e-3) * n + n) % n;}
ll pow(ll a, ll b, ll n){
ll d = 1;
a %= n;
while(b){
if(b & 1) d = mul(d, a, n);
a = mul(a, a, n);
b >>= 1;
}
return d;
}
bool check(ll a, ll n){
ll m = n - 1, x, y; int i, j = 0;
while(! (m & 1)) m >>= 1, j ++;
x = pow(a, m, n);
for(i = 1; i <= j; x = y, i ++){
y = pow(x, 2, n);
if((y == 1) && (x != 1) && (x != n - 1)) return 1;
}
return y != 1;
}
bool miller_rabin(int times, ll n){
ll a;
if(n == 1) return 0;
if(n == 2) return 1;
if(! (n & 1)) return 0;
while(times --) if(check(rand() % (n - 1) + 1, n)) return 0;
return 1;
}
ll pollard_rho(ll n, int c){
ll i = 1, k = 2, x = rand() % n, y = x, d;
while(1){
i ++, x = (mul(x, x, n) + c) % n, d = gcd(y - x, n);
if(d > 1 && d < n) return d;
if(y == x) return n;
if(i == k) y = x, k <<= 1;
}
}
void findfac(ll n, int c){
if(n == 1) return;
if(miller_rabin(S, n)){
pool[++cnt]=n;
return;
}
ll m = n;
while(m == n) m = pollard_rho(n, c --);
findfac(m, c), findfac(n / m, c);
}
ll num[222222];
ll nowp[50];
ll pw[50][100];
int lim[50];
int tot;
int now[50];
int cntdiv;
ll divisor[3000000];
int f[3000000];
void dfs(int x,ll y){
if(x==tot){
divisor[++cntdiv]=y;
return;
}
for(int i=0;i<=lim[x];i++)dfs(x+1,y*pw[x][i]);
}
inline int getid(ll x){return lower_bound(divisor+1,divisor+cntdiv+1,x)-divisor;}
void solve(int S){
int i,j,k;
if(num[S]==1)return;
cnt=0;
findfac(num[S],C);
sort(pool+1,pool+cnt+1);len[S]=0;
for(j=1;j<=cnt;j=k){
for(k=j;k<=cnt&&pool[j]==pool[k];k++);
pr[S][len[S]][0]=pool[j];
pr[S][len[S]][1]=k-j;
len[S]++;
}
tot=len[S];
for(j=0;j<tot;j++){
nowp[j]=pr[S][j][0];
lim[j]=pr[S][j][1];
for(pw[j][0]=k=1;k<=lim[j];k++){
pw[j][k]=pw[j][k-1]*nowp[j];
}
}
cntdiv=0;
dfs(0,1);
sort(divisor+1,divisor+cntdiv+1);
for(i=1;i<=cntdiv;i++)f[i]=0;
for(i=1;i<=n;i++){
ll val=1;
ll x=num[i];
for(k=0;k<tot;k++)if(x%nowp[k]==0){
int B=0;
while(x%nowp[k]==0)x/=nowp[k],B++;
val*=pw[k][min(B,lim[k])];
}
f[getid(val)]++;
}
for(i=0;i<tot;i++){
int x=nowp[i];
for(j=k=cntdiv;j;j--)if(divisor[j]%x==0){
ll goal=divisor[j]/x;
while(divisor[k]>goal)k--;
f[k]+=f[j];
}
}
for(i=1;i<=cntdiv;i++)if(f[i]>=m)ans=max(ans,divisor[i]);
}
int main(){
scanf("%d%d",&n,&m);
m=n-m;//keep >=m numbers
for(i=1;i<=n;i++){
ll x;
scanf("%lld",&x);
num[i]=x;
/*cnt=0;
findfac(x,C);
sort(pool+1,pool+cnt+1);
for(j=1;j<=cnt;j=k){
for(k=j;k<=cnt&&pool[j]==pool[k];k++);
pr[i][len[i]][0]=pool[j];
pr[i][len[i]][1]=k-j;
len[i]++;
}*/
}
ans=1;
for(int ___=8;___;___--){
int x=rand()%n+1;
solve(x);
}
printf("%lld",ans);
}
G. Berland Post
二分$T$，差分約束判負環。
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
const int N=1010,M=2010,LIM=1000000000;
const double eps=1e-8;
int n,m,i,unsure[N],a[N];
int e[M][3];
double L,R,ans,MID;
char s[100];
double d[N];
bool in[N];
int vis[N];
int q[10000010],h,t;
int g[N],v[M],nxt[M],ed;
double w[M];
inline void add(int x,int y,double z){v[++ed]=y;w[ed]=z;nxt[ed]=g[x];g[x]=ed;}
bool check(double T){
int i,j,x;
ed=0;
for(i=1;i<=n;i++)g[i]=0;
for(i=1;i<=m;i++)add(e[i][1],e[i][0],T-e[i][2]);
for(i=1;i<=n;i++)if(unsure[i])d[i]=LIM;else d[i]=a[i];
for(h=1,t=0,i=1;i<=n;i++)in[i]=1,q[++t]=i,vis[i]=0;
while(h<=t){
x=q[h++];
for(i=g[x];i;i=nxt[i])if(d[x]+w[i]+eps<d[v[i]]){
d[v[i]]=d[x]+w[i];
if(!in[v[i]]){
in[v[i]]=1;
vis[v[i]]++;
if(vis[v[i]]>3100)return 0;
q[++t]=v[i];
}
}
in[x]=0;
}
for(i=1;i<=n;i++){
if(d[i]+eps<-LIM)return 0;
if(!unsure[i]&&fabs(d[i]-a[i])>eps)return 0;
}
return 1;
}
int main(){
while(~scanf("%d%d",&n,&m)){
for(i=1;i<=n;i++){
scanf("%s",s);
if(s[0]=='?')unsure[i]=1;else{
unsure[i]=0;
sscanf(s,"%d",&a[i]);
}
}
for(i=1;i<=m;i++)scanf("%d%d%d",&e[i][0],&e[i][1],&e[i][2]);
L=0,R=LIM;
for(int i=77;i--;){
MID=(L+R)/2;
if(check(MID))R=(ans=MID);else L=MID;
}
check(ans);
printf("%.10f\n",ans);
for(i=1;i<=n;i++)printf("%.10f ",d[i]);
puts("");
}
}
H. Compressed Spanning Subtrees
對於每個點$i$詢問除它之外$n-1$個點的虛樹大小即可判斷出$i$是否是葉子。
選擇某個葉子$x$作為根，列舉一個葉子$y$以及一個非葉子$z$，詢問$x,y,z$的虛樹大小即可判斷出$y$是否在$z$的子樹中，並可以以此計算每個點子樹中的葉子個數。
因為題目保證不存在度數為$2$的點，故每個葉子往上到根路徑上每個點的子樹內葉子數嚴格遞增，排序即可完成構造。
#include<cstdio>
#include<algorithm>
#include<vector>
using namespace std;
const int N=110;
int n,i,j,is[N],root,size[N];
vector<int>pre[N];
int fa[N],vis[N],ans[N];
inline bool cmp(int x,int y){return size[x]>size[y];}
void dfs(int x,int y){
if(vis[x])return;
vis[x]=1;
ans[x]=y;
for(int i=1;i<=n;i++)if(fa[i]==x)dfs(i,x);
if(fa[x])dfs(fa[x],x);
}
int main(){
scanf("%d",&n);
if(n==2)return puts("! 1"),0;
for(i=1;i<=n;i++){
printf("? %d",n-1);
for(j=1;j<=n;j++)if(i!=j)printf(" %d",j);
puts("");
fflush(stdout);
scanf("%d",&is[i]);
is[i]=is[i]==n-1;
if(is[i])root=i;
}
size[root]=N;
for(i=1;i<=n;i++)if(!is[i])for(j=1;j<=n;j++)if(j!=root&&is[j]){
printf("? 3 %d %d %d\n",root,i,j);
fflush(stdout);
int t;
scanf("%d",&t);
if(t==3)size[i]++,pre[j].push_back(i);
}
for(i=1;i<=n;i++)if(i!=root&&is[i]){
pre[i].push_back(root);
pre[i].push_back(i);
sort(pre[i].begin(),pre[i].end(),cmp);
for(j=1;j<pre[i].size();j++)fa[pre[i][j]]=pre[i][j-1];
}
dfs(1,0);
printf("!");
for(i=2;i<=n;i++)printf(" %d",ans[i]);
}
I. Prefix-free Queries
對於一個$k$個子串的詢問，將這些串按照字典序排序，那麼可以用棧建出字首關係的樹結構，然後就是經典樹形DP。
時間複雜度$O(k\log k\log n)$。
#include<cstdio>
#include<algorithm>
using namespace std;
typedef pair<int,int>E;
const int N=400010,SEED=233,SEED2=13331,MO1=998244353,MO2=1000000007;
int n,m,i,k,mo,q[N],cnt[N],t,g[N],nxt[N],dp[N];
char a[N];
int f[N],p[N];
struct P{
int l,r,len;
}b[N];
inline int get(int l,int r){return
((f[r]-1LL*f[l-1]*p[r-l+1])%MO1+MO1)%MO1;
}
inline int lcp(int a,int b,int c,int d){
int l=1,r=min(b-a+1,d-c+1),mid,t=0;
while(l<=r){
mid=(l+r)>>1;
if(get(a,a+mid-1)==get(c,c+mid-1))l=(t=mid)+1;else r=mid-1;
}
//printf("[%d,%d] [%d,%d] %d\n",a,b,c,d,t);
return t;
}
inline bool cmp(const P&_a,const P&_b){//a<b?
int t=lcp(_a.l,_a.r,_b.l,_b.r);
if(t==_a.len){
if(_a.len==_b.len)return 0;//equal
return 1;//a is prefix of b
}
if(t==_b.len)return 0;//b is prefix of a
return a[_a.l+t]<a[_b.l+t];
}
inline bool equal(const P&a,const P&b){
int t=lcp(a.l,a.r,b.l,b.r);
if(t==a.len&&a.len==b.len)return 1;
return 0;
}
inline bool isprefix(const P&a,const P&b){
int t=lcp(a.l,a.r,b.l,b.r);
if(t==a.len)return 1;
return 0;
}
inline void add(int x,int y){
//printf("%d->%d\n",x,y);
nxt[y]=g[x];g[x]=y;}
void dfs(int x){
dp[x]=1;
for(int i=g[x];i;i=nxt[i]){
dfs(i);
dp[x]=1LL*dp[x]*dp[i]%mo;
}
dp[x]=(dp[x]+cnt[x])%mo;
//printf("dp[%d]=%d\n",x,dp[x]);
}
int main(){
scanf("%d%d%s",&n,&m,a+1);
for(p[0]=i=1;i<=n;i++){
p[i]=1LL*p[i-1]*SEED%MO1;
f[i]=(1LL*f[i-1]*SEED+a[i])%MO1;
}
while(m--){
scanf("%d%d",&k,&mo);
for(i=1;i<=k;i++)scanf("%d%d",&b[i].l,&b[i].r),b[i].len=b[i].r-b[i].l+1;
sort(b+1,b+k+1,cmp);
for(i=0;i<=k;i++)g[i]=0;
cnt[0]=1;
for(t=0,i=1;i<=k;i++){
if(t&&equal(b[q[t]],b[i])){
cnt[q[t]]++;
continue;
}
while(t&&!isprefix(b[q[t]],b[i]))t--;
add(q[t],i);
q[++t]=i;
cnt[i]=1;
}
//for(i=1;i<=k;i++)printf("cnt[%d]=%d\n",i,cnt[i]);
dfs(0);
printf("%d\n",((dp[0]-1)%mo+mo)%mo);
}
}
/*
10 100
aabbaacaba
5 20 1 2 3 4 5 6 7 8 9 10
*/
J. Subsequence Sum Queries
分治，預處理出$mid$到$[l,r]$每個點的揹包，然後利用這個資訊處理所有經過$mid$的詢問。
時間複雜度$O((nm+q)\log n+qm)$。
#include<cstdio>
#include<vector>
using namespace std;
typedef vector<int>V;
const int N=200010,M=25,P=1000000007;
int n,m,Q,i,a[N],f[N][M],g[N][M],e[N][3];
inline void up(int&a,int b){a=a+b<P?a+b:a+b-P;}
void solve(int l,int r,V v){
if(l>r||!v.size())return;
int mid=(l+r)/2;
//[i..mid] [mid+1..i]
for(int i=l;i<=mid+1;i++)for(int j=0;j<m;j++)f[i][j]=0;
f[mid+1][0]=1;
for(int i=mid;i>=l;i--){
for(int j=0;j<m;j++){
up(f[i][j],f[i+1][j]);
up(f[i][(j+a[i])%m],f[i+1][j]);
}
}
for(int i=mid;i<=r;i++)for(int j=0;j<m;j++)g[i][j]=0;
g[mid][0]=1;
for(int i=mid+1;i<=r;i++){
for(int j=0;j<m;j++){
up(g[i][j],g[i-1][j]);
up(g[i][(j+a[i])%m],g[i-1][j]);
}
}
V vl,vr;
for(int i=0;i<v.size();i++){
int x=v[i];
if(e[x][0]>mid)vr.push_back(x);
else if(e[x][1]<mid)vl.push_back(x);
else{
for(int j=0;j<m;j++)up(e[x][2],1LL*f[e[x][0]][j]*g[e[x][1]][(m-j)%m]%P);
}
}
solve(l,mid-1,vl);
solve(mid+1,r,vr);
}
int main(){
scanf("%d%d",&n,&m);
for(i=1;i<=n;i++)scanf("%d",&a[i]),a[i]%=m;
scanf("%d",&Q);
V _;
for(i=1;i<=Q;i++){
scanf("%d%d",&e[i][0],&e[i][1]);
_.push_back(i);
}
solve(1,n,_);
for(i=1;i<=Q;i++)printf("%d\n",e[i][2]);
}
K. Consistent Occurrences
將詢問按長度分組，則最多隻有$O(\sqrt{n})$種長度，對於每種長度$O(n\log n)$計算答案即可。
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<map>
using namespace std;
typedef long long ll;
typedef pair<ll,ll>PI;
typedef pair<PI,int>P;
const int N=100010,SEED=233,SEED2=13331,MO=998244353,MO2=1000000007;
int n,m,i,j;
char a[N],b[N];
ll p[N],f[N],p2[N],f2[N];
map<PI,int>T[N],have[N];
bool vis[N];
P e[N],q[N];
inline PI get(int l,int r){
return PI(
((f[r]-f[l-1]*p[r-l+1])%MO+MO)%MO,
((f2[r]-f2[l-1]*p2[r-l+1])%MO2+MO2)%MO2
);
}
inline void make(int l,int r,const P&o,int len){
if(have[len].find(o.first)==have[len].end())return;
int i,pre=-N,cnt=0;
for(i=l;i<=r;i++){
if(e[i].second-pre>=len){
cnt++;
pre=e[i].second;
}
}
T[len][o.first]=cnt;
}
void pre(int len){
int i,j,cnt=0;
vis[len]=1;
for(i=len;i<=n;i++){
e[++cnt]=P(get(i-len+1,i),i);
}
sort(e+1,e+cnt+1);
for(i=1;i<=cnt;i=j){
for(j=i;j<=cnt&&e[i].first==e[j].first;j++);
make(i,j-1,e[i],len);
}
}
inline int ask(int len,PI goal){
if(!vis[len])pre(len);
return T[len][goal];
}
int main(){
scanf("%d%d%s",&n,&m,a+1);
for(p[0]=i=1;i<=n;i++)p[i]=p[i-1]*SEED%MO;
for(i=1;i<=n;i++)f[i]=(f[i-1]*SEED+a[i])%MO;
for(p2[0]=i=1;i<=n;i++)p2[i]=p2[i-1]*SEED2%MO2;
for(i=1;i<=n;i++)f2[i]=(f2[i-1]*SEED2+a[i])%MO2;
for(j=1;j<=m;j++){
scanf("%s",b+1);
ll now=0,now2=0;
int len=strlen(b+1);
for(i=1;i<=len;i++)now=(now*SEED+b[i])%MO;
for(i=1;i<=len;i++)now2=(now2*SEED2+b[i])%MO2;
have[len][PI(now,now2)]=1;
q[j]=P(PI(now,now2),len);
}
for(j=1;j<=m;j++){
printf("%d\n",ask(q[j].second,q[j].first));
}
}
/*
8 8888
abaabbab
ab
3
aa
0
*/
L. Increasing Costs
建出最短路圖後，將每條邊拆點，那麼答案就是每條邊代表的點在Dominator Tree中的子樹大小。
#include<cstdio>
typedef long long ll;
const int N=500010,M=1000010,K=22;
const ll inf=1LL<<60;
int n,m,S,cnt,i,x,deg[N],g[N],v[M],w[M],nxt[M],ed;
int size[N],sum[N],id[N],h,t,q[N],dep[N],f[N][K],G[N],NXT[N],V[N];
ll d[N];
struct E{int x,y,w;}a[M>>1];
inline void read(int&a){char c;while(!(((c=getchar())>='0')&&(c<='9')));a=c-'0';while(((c=getchar())>='0')&&(c<='9'))(a*=10)+=c-'0';}
inline void addedge(int x,int y,int z){v[++ed]=y;w[ed]=z;nxt[ed]=g[x];g[x]=ed;}
inline void add(int x,int y){deg[y]++;v[++ed]=y;nxt[ed]=g[x];g[x]=ed;}
inline void addtree(int x,int y){V[++ed]=y;NXT[ed]=G[x];G[x]=ed;}
struct PI{
ll x;int y;
PI(){}
PI(ll _x,int _y){x=_x,y=_y;}
inline PI operator+(const PI&b){return x<=b.x?PI(x,y):b;}
}val[2222222];
void build(int x,int a,int b){
val[x]=PI(inf,a);
if(a==b)return;
int mid=(a+b)>>1;
build(x<<1,a,mid),build(x<<1|1,mid+1,b);
}
inline void change(int x,int a,int b,int c,ll d){
if(a==b){val[x].x=d;return;}
int mid=(a+b)>>1;
c<=mid?change(x<<1,a,mid,c,d):change(x<<1|1,mid+1,b,c,d);
val[x]=val[x<<1]+val[x<<1|1];
}
inline int lca(int x,int y){
int i;
if(dep[x]<dep[y])i=x,x=y,y=i;
for(i=K-1;~i;i--)if(dep[f[x][i]]>=dep[y])x=f[x][i];
if(x==y)return x;
for(i=K-1;~i;i--)if(f[x][i]!=f[y][i])x=f[x][i],y=f[y][i];
return f[x][0];
}
void dfs(int x){
for(int i=G[x];i;i=NXT[i])dfs(V[i]),size[x]+=size[V[i]];
sum[id[x]]=size[x];
}
int main(){
read(n),read(m);
for(i=1;i<=m;i++){
read(a[i].x),read(a[i].y),read(a[i].w);
addedge(a[i].x,a[i].y,a[i].w);
addedge(a[i].y,a[i].x,a[i].w);
}
S=1;
for(i=1;i<=n;i++)d[i]=inf;
build(1,1,n),change(1,1,n,S,d[S]=0);
while(val[1].x<inf)for(change(1,1,n,x=val[1].y,inf),i=g[x];i;i=nxt[i])if(d[x]+w[i]<d[v[i]])change(1,1,n,v[i],d[v[i]]=d[x]+w[i]);
for(ed=0,i=1;i<=n;i++)g[i]=0,size[i]=d[i]<inf;
for(cnt=n,i=1;i<=m;i++){
if(d[a[i].x]+a[i].w==d[a[i].y])id[++cnt]=i,add(a[i].x,cnt),add(cnt,a[i].y);
if(d[a[i].y]+a[i].w==d[a[i].x])id[++cnt]=i,add(a[i].y,cnt),add(cnt,a[i].x);
}
for(cnt++,i=1;i<cnt;i++)if(!deg[i])add(cnt,i);
q[h=t=1]=cnt,ed=0;
while(h<=t){
x=q[h++];
if(f[x][0])addtree(f[x][0],x);
for(dep[x]=dep[f[x][0]]+1,i=1;i<K;i++)f[x][i]=f[f[x][i-1]][i-1];
for(i=g[x];i;i=nxt[i]){
if(!f[v[i]][0])f[v[i]][0]=x;else f[v[i]][0]=lca(f[v[i]][0],x);
if(!(--deg[v[i]]))q[++t]=v[i];
}
}
dfs(cnt);
for(i=1;i<=m;i++)printf("%d\n",sum[i]);
}