Markdown 谢谢：
by Retired_lvmao @ 2019-06-16 11:34:41
希望更丰富的展现？使用Markdown
by charliegong @ 2019-06-16 11:39:19
```cpp
#include <bits/stdc++.h>
using namespace std;
long long bb[5001][5001];
double power(double a,long long b) {
double ans=1;
while(b>0) {
if(b&1) ans=ansa;
a=aa;
b>>=1;
}
return ans;
}
void lala() {
bb[1][1]=1;
for (int i=2; i<=51; i++) for (int j=1; j<=i; j++) bb[i][j]=(bb[i-1][j-1]+bb[i-1][j]);
}
int main() {
int n,q;
double a;
long long sum1=0,sum0=0;
double sum2=0,sum3=0;
cin>>n>>a>>q;
double aa=a/100;
string s;
cin>>s;
for(int i=0; i<n; i++) {
if(s[i]=='1') sum1++;
if(s[i]=='0') sum0++;
}
if(n>50) {
sum2=1;
printf("%.3lf",sum2);
return 0;
}
if(n<=50) {
for(int i=1; i<=51; i++) bb[i][0]=1;
lala();
for(int i=0; i<=sum1; i++) for(int j=0; j<=sum0; j++) {
if(i+j>=q) {
double ans=bb[sum1][i]power(aa,i)power(1-aa,sum1-i);
double ans1=bb[sum0][j]power(1-aa,j)power(aa,sum0-j);
sum3+=ans*ans1;
}
}
printf("%.3lf",sum3);
}
return 0;
}
```
by Elijah_ @ 2019-10-14 20:20:01
# 不用谢,我叫雷锋
@[帅宝](/space/show?uid=105943)
by Elijah_ @ 2019-10-14 20:21:13
组合数 bb[0][0] = 1
by RQ。。。 @ 2021-07-12 18:10:28
考古，谢谢兄弟们
by 帅宝 @ 2021-09-24 21:29:19
考古
by Plenilune_Dreamer @ 2023-09-19 16:32:11