NOIP 模拟 $36\; \rm Cicada 与排序$
2021/8/13 6:36:14
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题解 \(by\;zj\varphi\)
设 \(rk_{i,j}\) 表示第 \(i\) 个数最后在相同的数里排第 \(j\) 位的概率。
转移时用一个 \(dp\),\(dp_{i,j,0/1}\) 表示归并排序时第一个数组弹了 \(i\) 个,第二个数组弹了 \(j\) 个,最后一个弹的是第一个数组的还是第二个的。
直接模拟归并排序,然后在过程中枚举值域即可。
Code
#include<bits/stdc++.h> #define Re register #define ri register signed #define p(i) ++i namespace IO{ char buf[1<<21],*p1=buf,*p2=buf; #define gc() p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?(-1):*p1++ struct nanfeng_stream{ template<typename T>inline nanfeng_stream operator>>(T &x) { ri f=0;x=0;register char ch=gc(); while(!isdigit(ch)) f|=ch=='-',ch=gc(); while(isdigit(ch)) x=(x<<1)+(x<<3)+(ch^48),ch=gc(); return x=f?-x:x,*this; } }cin; } using IO::cin; namespace nanfeng{ #define pb push_back #define FI FILE *IN #define FO FILE *OUT template<typename T>inline T cmax(T x,T y) {return x>y?x:y;} template<typename T>inline T cmin(T x,T y) {return x>y?y:x;} typedef long long ll; static const int N=501,MOD=998244353,inv=499122177; std::vector<int> lT[N<<1],rT[N<<1]; int a[N],lcnt[N<<1],rcnt[N<<1],mx,n; ll rk[N][N],tmp[N],dp[N][N][2]; void mergesort(int l,int r) { if (l==r) return; int mid(l+r>>1); mergesort(l,mid); mergesort(mid+1,r); for (ri i(l);i<=mid;p(i)) ++lcnt[a[i]],lT[a[i]].pb(i); for (ri i(mid+1);i<=r;p(i)) ++rcnt[a[i]],rT[a[i]].pb(i); for (ri i(1);i<=mx;p(i)) { for (ri l(0);l<=lcnt[i];p(l)) for (ri r(0);r<=rcnt[i];p(r)) dp[l][r][0]=dp[l][r][1]=0; dp[0][0][0]=1; for (ri l(0);l<=lcnt[i];p(l)) for (ri r(0);r<=rcnt[i];p(r)) if (l!=lcnt[i]&&r!=rcnt[i]) dp[l+1][r][0]=(dp[l+1][r][0]+(dp[l][r][0]+dp[l][r][1])*inv)%MOD, dp[l][r+1][1]=(dp[l][r+1][1]+(dp[l][r][0]+dp[l][r][1])*inv)%MOD; else if (l!=lcnt[i]) dp[l+1][r][0]=(dp[l+1][r][0]+dp[l][r][0]+dp[l][r][1])%MOD; else if (r!=rcnt[i]) dp[l][r+1][1]=(dp[l][r+1][1]+dp[l][r][0]+dp[l][r][1])%MOD; for (ri j(0);j<lcnt[i];p(j)) { for (ri k(1);k<=lcnt[i];p(k)) for (ri r(0);r<=rcnt[i];p(r)) tmp[k+r]=(tmp[k+r]+rk[lT[i][j]][k]*dp[k][r][0])%MOD; for (ri nrk(1);nrk<=lcnt[i]+rcnt[i];p(nrk)) rk[lT[i][j]][nrk]=tmp[nrk],tmp[nrk]=0; } for (ri j(0);j<rcnt[i];p(j)) { for (ri k(1);k<=rcnt[i];p(k)) for (ri l(0);l<=lcnt[i];p(l)) tmp[k+l]=(tmp[k+l]+rk[rT[i][j]][k]*dp[l][k][1])%MOD; for (ri nrk(1);nrk<=lcnt[i]+rcnt[i];p(nrk)) rk[rT[i][j]][nrk]=tmp[nrk],tmp[nrk]=0; } lT[i].clear(),rT[i].clear(); lcnt[i]=rcnt[i]=0; } } inline int main() { //FI=freopen("nanfeng.in","r",stdin); //FO=freopen("nanfeng.out","w",stdout); cin >> n; for (ri i(1);i<=n;p(i)) cin >> a[i],mx=cmax(mx,a[i]); for (ri i(1);i<=n;p(i)) rk[i][1]=1; mergesort(1,n); for (ri i(1);i<=n;p(i)) ++lcnt[a[i]]; for (ri i(1);i<=mx;p(i)) lcnt[i]+=lcnt[i-1]; for (ri i(1);i<=n;p(i)) { Re ll ans(0); for (ri j(1);j<=lcnt[a[i]]-lcnt[a[i]-1];p(j)) ans=(ans+rk[i][j]*j)%MOD; printf("%lld ",ans+lcnt[a[i]-1]); } return 0; } } int main() {return nanfeng::main();}
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