coding/HashingTemplate at master · chayankumar999/coding · GitHub

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/*
********************Primes*********************
1000000007, 998244353,  777767777, 492366587, 1645333507, 909090909090909091, 108086391056891903

*/

#include<bits/stdc++.h>
using namespace std;
#define FasterIO ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)

typedef unsigned long long ull;
typedef long long ll;

const int MX=1000000+5;

struct HASH
{
    ull base=31, pw[MX], H[MX], RH[MX];
    int n;
    void generate_hash(string s)
    {
        pw[0]=1; n=s.size();

        // generate power of base value
        for(int i=1; i<=n; i++) pw[i]=(pw[i-1]*base);

        // generate front hash
        for(int i=0; i<n; i++)  H[i+1]  = ( i ? ( H[i] * base ) : 0 ) + s[i];

        //generate reverse hash
        for(int i=0; i<n; i++)  RH[i+1] = ( i ? (RH[i] * base ) : 0 ) + s[n-i-1];
    }

    ull getHV(int i, int sz) // return front hash between a range
    {
        return H[i+sz] - H[i] * pw[sz];
    }
    ull getRHV(int i, int sz) // return reverse hash between a range
    {
        return RH[i+sz] - RH[i] * pw[sz];
    }
    ull deleteChar(int i) // return hash value after deleting ith char
    {
        ull h = getHV(i+1, n-i-1);
        if(i) h = getHV(0, i) * pw[n-i-1] + h;
        return h;
    }

}HS;

struct HASH2
{
    ll base=31, mod=1e9+7, pw[MX], H[MX], RH[MX], n, m;

    void generate_hash(string s)
    {
        pw[0]=1; n=s.size();

        for(int i=1; i<=n; i++) pw[i] = (pw[i-1] * base ) % mod;

        for(int i=0; i<n; i++)  H[i+1]  = ( ( i ? ( H[i] * base ) : 0 ) + s[i]) % mod;

        for(int i=0; i<n; i++)  RH[i+1] = ( ( i ? (RH[i] * base ) : 0 ) + s[n-i-1]) % mod;
    }

    ll getHV(int i, int sz)
    {
        return (H[i+sz] - (H[i] * pw[sz]) % mod + mod) % mod;
    }
    ll getRHV(int i, int sz)
    {
        return (RH[i+sz] - (RH[i] * pw[sz]) % mod + mod) % mod;
    }
    ll deleteChar(int i)
    {
        ll h = getHV(i+1, n-i-1);
        if(i) h = ((getHV(0, i) * pw[n-i-1]) % mod + h)%mod;
        return h;
    }

}HS2;

int main()
{
    FasterIO;

    int n; string s;

    cin>>s; n=s.size();

    HS2.generate_hash(s);

    ll HH=HS2.getRHV(0, n);

    ll H=HS2.deleteChar(0 /*i*/);

    return 0;
}