CF991E Bus Number

Translation of the meaning of problems

Give you a digital sequence A (length of no more than 18), asked how many sequences B satisfy ①A all figures are sure to appeared in B; ② B all the numbers must also be appeared in A; ③ sequence B can not begin with 0

Input # 1

97

Output # 1

2

Problem-solving ideas

 To count the number of each of a sequence number that appears in the input string can then turn into type int, may be directly scanf ( "% 1d", & a);

Then each digit appears dfs case

Direct sleeve formula ans + = factorial of the number of all the numbers / factorial of the number of digits in each of the first product of a case -0

AC Code

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int num[10],temp[10];
ll jc[20],ans=0;
void dfs(int x) {
    if(x==10) {
        int cnt=0;
        for(int i=0; i<10; ++i) cnt += temp[i];
        ll p=jc[cnt];
        for(int i=0; i<10; ++i) p/=jc[temp[i]];
        if(temp[0]>=1) p-=(p*temp[0]/cnt);
        ans+=p;
        return;
    }
    for(int i=1; i<=num[x]; ++i) {
        temp[x]=i;
        dfs(x+1);
    }
    if(num[x]==0) dfs(x+1);
}

int main() {
    int a;
    while(scanf("%1d",&a)!=EOF){
        num[a]++;
    }
    jc[0]=1;
    for(int i=1; i<=19; i++) jc[i]=jc[i-1]*i;
    dfs(0);
    cout<<ans<<endl;
    return 0;
}