Submission #4575066
Source Code Expand
/* AT2705 Yes or No n为yes的题数,m为no的题数 当n>m的时候,猜yes 当n<m的时候,猜no 这样猜一定能保证猜对max(n,m)次 考虑n=m时猜对的期望 猜对的概率(对答案的贡献)是n/(n+m)=1/2 考虑走到(i,i)这个点的方案数 C(2i,i)*(n-i+m-i,n-i) 前2i步钦定i步向右走(剩余i步向上走) 后n-i+m-i步钦定n-i步向右走(剩余m-i步向上走),以免走出网格 故走到(i,i)的概率是sigma(C(2i,i)*(n-i+m-i,n-i))/C(n+m,n) C(n+m,n)是总方案数 当n=m时的期望贡献是(1/2)*sigma(C(2i,i)*(n-i+m-i,n-i))/C(n+m,n) i=1~min(n,m) */ #include <cstdio> typedef long long ll; #define ri register int #pragma GCC optimize(1) #pragma GCC optimize(2) #pragma GCC optimize(3) #pragma GCC optimize("Ofast") const int N=1000005,mod=998244353; int fac[N],inv[N]; inline int C(ri n,ri m){ return (ll)fac[n]*inv[m]%mod*inv[n-m]%mod; } inline int max(ri x,ri y){ return x>y ? x:y; } inline int min(ri x,ri y){ return x<y ? x:y; } inline void add(int &x,ri y){ x+=y; if(x>=mod) x-=mod; } inline int Pow(ri a,ri b){ ri ans=1; for(;b;b>>=1,a=(ll)a*a%mod) if(b&1) ans=(ll)ans*a%mod; return ans; } int main(){ ri n,m,i,sum,yes; scanf("%d%d",&n,&m); sum=n+m; fac[0]=inv[0]=1; for(i=1;i<=sum;++i) fac[i]=(ll)fac[i-1]*i%mod; inv[sum]=Pow(fac[sum],mod-2); for(i=sum-1;i;--i) inv[i]=(ll)inv[i+1]*(i+1)%mod; yes=0; for(i=min(n,m);i;--i) add(yes,(ll)C(2*i,i)*C(n-i+m-i,n-i)%mod); yes=(ll)yes*Pow(C(n+m,n),mod-2)%mod*inv[2]%mod; add(yes,max(n,m)); printf("%d\n",yes); return 0; }
Submission Info
Submission Time | |
---|---|
Task | F - Yes or No |
User | luogu_bot5 |
Language | C++ (GCC 5.4.1) |
Score | 2000 |
Code Size | 1607 Byte |
Status | AC |
Exec Time | 18 ms |
Memory | 7936 KB |
Compile Error
./Main.cpp: In function ‘int main()’: ./Main.cpp:47:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^
Judge Result
Set Name | Sample | Partial | All | ||||||
---|---|---|---|---|---|---|---|---|---|
Score / Max Score | 0 / 0 | 1500 / 1500 | 500 / 500 | ||||||
Status |
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Set Name | Test Cases |
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Sample | sample_01.txt, sample_02.txt, sample_03.txt, sample_04.txt, sample_05.txt |
Partial | sample_01.txt, sample_02.txt, sample_04.txt, subtask_1_01.txt, subtask_1_02.txt, subtask_1_03.txt, subtask_1_04.txt, subtask_1_05.txt, subtask_1_06.txt, subtask_1_07.txt, subtask_1_08.txt, subtask_1_09.txt, subtask_1_10.txt, subtask_1_11.txt, subtask_1_12.txt, subtask_1_13.txt, subtask_1_14.txt, subtask_1_15.txt, subtask_1_16.txt, subtask_1_17.txt, subtask_1_18.txt, subtask_1_19.txt, subtask_1_20.txt, subtask_1_21.txt, subtask_1_22.txt, subtask_1_23.txt, subtask_1_24.txt, subtask_1_25.txt |
All | sample_01.txt, sample_02.txt, sample_03.txt, sample_04.txt, sample_05.txt, sample_01.txt, sample_02.txt, sample_03.txt, sample_04.txt, sample_05.txt, subtask_1_01.txt, subtask_1_02.txt, subtask_1_03.txt, subtask_1_04.txt, subtask_1_05.txt, subtask_1_06.txt, subtask_1_07.txt, subtask_1_08.txt, subtask_1_09.txt, subtask_1_10.txt, subtask_1_11.txt, subtask_1_12.txt, subtask_1_13.txt, subtask_1_14.txt, subtask_1_15.txt, subtask_1_16.txt, subtask_1_17.txt, subtask_1_18.txt, subtask_1_19.txt, subtask_1_20.txt, subtask_1_21.txt, subtask_1_22.txt, subtask_1_23.txt, subtask_1_24.txt, subtask_1_25.txt, subtask_2_01.txt, subtask_2_02.txt, subtask_2_03.txt, subtask_2_04.txt, subtask_2_05.txt, subtask_2_06.txt, subtask_2_07.txt, subtask_2_08.txt, subtask_2_09.txt, subtask_2_10.txt, subtask_2_11.txt, subtask_2_12.txt, subtask_2_13.txt, subtask_2_14.txt, subtask_2_15.txt, subtask_2_16.txt, subtask_2_17.txt, subtask_2_18.txt, subtask_2_19.txt, subtask_2_20.txt, subtask_2_21.txt, subtask_2_22.txt, subtask_2_23.txt, subtask_2_24.txt, subtask_2_25.txt, subtask_2_26.txt, subtask_2_27.txt, subtask_2_28.txt, subtask_2_29.txt, subtask_2_30.txt, subtask_2_31.txt, subtask_2_32.txt, subtask_2_33.txt, subtask_2_34.txt, subtask_2_35.txt, subtask_2_36.txt, subtask_2_37.txt, subtask_2_38.txt, subtask_2_39.txt, subtask_2_40.txt |
Case Name | Status | Exec Time | Memory |
---|---|---|---|
sample_01.txt | AC | 1 ms | 2176 KB |
sample_02.txt | AC | 1 ms | 2176 KB |
sample_03.txt | AC | 1 ms | 2176 KB |
sample_04.txt | AC | 1 ms | 2176 KB |
sample_05.txt | AC | 1 ms | 2176 KB |
subtask_1_01.txt | AC | 1 ms | 2176 KB |
subtask_1_02.txt | AC | 1 ms | 2176 KB |
subtask_1_03.txt | AC | 1 ms | 2176 KB |
subtask_1_04.txt | AC | 1 ms | 2176 KB |
subtask_1_05.txt | AC | 1 ms | 2176 KB |
subtask_1_06.txt | AC | 1 ms | 2176 KB |
subtask_1_07.txt | AC | 1 ms | 2176 KB |
subtask_1_08.txt | AC | 1 ms | 2176 KB |
subtask_1_09.txt | AC | 1 ms | 2176 KB |
subtask_1_10.txt | AC | 1 ms | 2176 KB |
subtask_1_11.txt | AC | 1 ms | 2176 KB |
subtask_1_12.txt | AC | 1 ms | 2176 KB |
subtask_1_13.txt | AC | 1 ms | 2304 KB |
subtask_1_14.txt | AC | 2 ms | 4480 KB |
subtask_1_15.txt | AC | 5 ms | 4992 KB |
subtask_1_16.txt | AC | 5 ms | 4992 KB |
subtask_1_17.txt | AC | 5 ms | 4992 KB |
subtask_1_18.txt | AC | 5 ms | 4992 KB |
subtask_1_19.txt | AC | 5 ms | 4992 KB |
subtask_1_20.txt | AC | 5 ms | 4992 KB |
subtask_1_21.txt | AC | 5 ms | 4992 KB |
subtask_1_22.txt | AC | 5 ms | 4992 KB |
subtask_1_23.txt | AC | 5 ms | 4992 KB |
subtask_1_24.txt | AC | 5 ms | 4992 KB |
subtask_1_25.txt | AC | 4 ms | 4992 KB |
subtask_2_01.txt | AC | 1 ms | 2176 KB |
subtask_2_02.txt | AC | 1 ms | 2176 KB |
subtask_2_03.txt | AC | 1 ms | 2176 KB |
subtask_2_04.txt | AC | 18 ms | 7936 KB |
subtask_2_05.txt | AC | 18 ms | 7936 KB |
subtask_2_06.txt | AC | 18 ms | 7936 KB |
subtask_2_07.txt | AC | 18 ms | 7936 KB |
subtask_2_08.txt | AC | 18 ms | 7936 KB |
subtask_2_09.txt | AC | 18 ms | 7936 KB |
subtask_2_10.txt | AC | 17 ms | 7936 KB |
subtask_2_11.txt | AC | 18 ms | 7936 KB |
subtask_2_12.txt | AC | 18 ms | 7936 KB |
subtask_2_13.txt | AC | 18 ms | 7936 KB |
subtask_2_14.txt | AC | 18 ms | 7936 KB |
subtask_2_15.txt | AC | 17 ms | 7936 KB |
subtask_2_16.txt | AC | 18 ms | 7936 KB |
subtask_2_17.txt | AC | 17 ms | 7936 KB |
subtask_2_18.txt | AC | 16 ms | 7680 KB |
subtask_2_19.txt | AC | 14 ms | 7168 KB |
subtask_2_20.txt | AC | 7 ms | 6272 KB |
subtask_2_21.txt | AC | 7 ms | 6144 KB |
subtask_2_22.txt | AC | 7 ms | 6272 KB |
subtask_2_23.txt | AC | 7 ms | 6144 KB |
subtask_2_24.txt | AC | 7 ms | 6272 KB |
subtask_2_25.txt | AC | 7 ms | 6144 KB |
subtask_2_26.txt | AC | 7 ms | 6272 KB |
subtask_2_27.txt | AC | 7 ms | 6272 KB |
subtask_2_28.txt | AC | 7 ms | 6272 KB |
subtask_2_29.txt | AC | 8 ms | 6272 KB |
subtask_2_30.txt | AC | 9 ms | 6400 KB |
subtask_2_31.txt | AC | 11 ms | 6784 KB |
subtask_2_32.txt | AC | 18 ms | 7936 KB |
subtask_2_33.txt | AC | 18 ms | 7936 KB |
subtask_2_34.txt | AC | 17 ms | 7936 KB |
subtask_2_35.txt | AC | 17 ms | 7936 KB |
subtask_2_36.txt | AC | 17 ms | 7936 KB |
subtask_2_37.txt | AC | 9 ms | 6144 KB |
subtask_2_38.txt | AC | 7 ms | 5888 KB |
subtask_2_39.txt | AC | 17 ms | 7808 KB |
subtask_2_40.txt | AC | 9 ms | 6400 KB |