字符串哈希

【用法】

　　将字符串的所有前缀表示为一个哈希值。

　　先设置成一个p进制 （ 一般取131 或者 13331 ） ， 哈希值R为2^64 次 （ 或者开 unsigned longlong 当做取模了）

【作用】

　　判断字符串的子串是否相等。

【代码】

　　

#include <bits/stdc++.h>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <string>
#include <vector>
#include <stack>
#include <bitset>
#include <cstdlib>
#include <cmath>
#include <set>

#define ms(a, b) memset(a,b,sizeof(a))
#define fast ios::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define ll long long
#define ull unsigned long long
#define rep(i, a, b)  for(ll i=a;i<=b;i++)
#define lep(i, a, b)  for(ll i=a;i>=b;i--)
#define endl '\n'
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vi  vector<ll>
#define vpi vector<pii>
#define vpl vector<pll>
#define mi  map<ll,ll>
#define all(a)  (a).begin(),(a).end()
#define gcd __gcd
#define pb push_back
#define mp make_pair
#define lb lower_bound
#define ub upper_bound

#define ff first
#define ss second
#define test4(x, y, z, a) cout<<"x is "<<x<<"        y is "<<y<<"        z is "<<z<<"        a is "<<a<<endl;
#define test3(x, y, z) cout<<"x is "<<x<<"        y is "<<y<<"        z is "<<z<<endl;
#define test2(x, y) cout<<"x is "<<x<<"        y is "<<y<<endl;
#define test1(x) cout<<"x is "<<x<<endl;
using namespace std;
const int N = 100010;
const int maxx = 0x3f3f3f;
const int mod = 1e9 + 7;
const int minn = -0x3f3f3f;
const int M = 2 * N;
const int P = 131 ;
ll T, n, m;
char s[N];
unsigned ll h[N],p[N];
unsigned ll getsr(int x,int y ){
    return h[y]-h[x-1]*p[y-x+1];
}
void solve() {
    cin>>n>>m;
    cin>>s+1;
    p[0] = 1 ;
    rep(i,1,n){
        h[i] = h[i-1] * P + s[i];
        p[i] = p[i-1] * P ;
    }
    while ( m-- ){
        int l1,l2,r1,r2;
        cin>>l1>>r1>>l2>>r2;
        if ( getsr(l1,r1) == getsr(l2,r2) ) cout<<"Yes"<<endl;
        else cout<<"No"<<endl;
    }
}
int main() {
    fast;
    solve();
    return 0;
}

【题目连接】

　　841. 字符串哈希 - AcWing题库