P12200 Hash Killer Extra 题解

· · 题解

啊?这题是数学构造?

```cpp #include <bits/stdc++.h> using namespace std; int b,p,k; string rnd(int n) { string s; for (int i=1;i<=n;++i) s+=char(rand()%26+'a'); return s; } int strhash(const string &s, int b, int p) { int val = 0; for (int i = 0; i < s.length(); i++) val = (1ll * val * b + s[i] - 'a' + 1) % p; return val; } string s; unordered_map<int,string> mp; int main() { cin>>b>>p; while (s=rnd(20),k=strhash(s,b,p)) { if (mp.count(k)&&mp[k]!=s) { cout<<mp[k]<<endl<<s<<endl; break; } else mp[k]=s; } } ```