康托展开
#include<iostream> #include<cmath> #include<algorithm> #include<cstring> #include<string> #include<stack> #include<queue> #include<map> #include<cstdlib> #include<set> #include<ctime> #include<vector> #include<cstdio> #include<list> using namespace std; typedef long long ll; int INF=2147483647; int inf=-2147483648; #define read(x) scanf("%d",&x); #define fo(i,n) for(int i=1;i<=(n);i++) #define me(a) memset(a,0,sizeof(a)); #define one(x) cout<<(x)<<endl; #define two(a,b) cout<<(a)<<" "<<(b)<<endl; int jiecheng(int r) { int p=1; for(int x=r;x>=1;x--) { p=p*x; } return p; } int a[100005]; int main() { int cnt; int ans=1; string s; me(a); cin>>s; for(int j=0;j<s.length();j++) { a[j]=s[j]-'a'+1; } for(int i=0;i<s.length();i++) { cnt=0; for(int j=i+1;j<s.length();j++) { if(a[i]>a[j]) cnt++; } ans+=(cnt*(jiecheng(s.length()-i-1))); } one(ans); return 0; }