字符串hash

#include<iostream>
#include<iomanip>
#include<cstdio>
#include<vector>
#include<cmath>
#include<string>
#include<cstring>
#include<algorithm>
#include<unordered_map>
#include<unordered_set>
#include<queue>
#include<map>
#include<set>
#define  endl '
'
#define all(s) s.begin(),s.end()
#define lowbit(x) (x&-x)
#define rep(i,a,n) for (int i=a;i<=n;i++)
#define IOS ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define mem(a,b) memset(a,b,sizeof(a))
#define fi first
#define se second
#define pb push_back
#define pi acos(-1.0)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
const int mod = 1e9 + 7;
const double eps = 1e-8;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const int N = 2e5 + 10;
const int maxn = 2e5 + 10;
struct ha{
    ull h[maxn],p[maxn], P = 131;
    void k_hash(string s)    {
        p[0]=1;
        h[0]=s[0];
        for(int i=1;i<s.size();i++){
            p[i]=p[i-1]*P;    //次方
            h[i]=h[i-1]*P+s[i];    //hash值
        }
    }
    ull get_hash(int left,int right){
        if(left > right) return 0;
        return left?h[right]-h[left-1]*p[right-left+1]:h[right];
    }
}hash1 , hash2;
int main()
{
    string s, t;
    cin >> s >> t;
    hash1.k_hash(s);
    hash2.k_hash(t);
    ll ans = 0;
    for(int i = 0; i < s.length(); i++){
        if(i >= t.length() - 1) break;
        if(hash1.get_hash(0, i) == hash2.get_hash(0, i)){
            int l = 0, r = min(t.length() - i - 1, s.length() - 1);
            while(l <= r){
                int mid = l + r >> 1;
                if(hash1.get_hash(0, mid) == hash2.get_hash(i + 1, i + 1 + mid)) l = mid + 1;
                else r = mid - 1;
            }
            ans += r + 1;
        }
    }
    cout << ans;
}