线段树维护字符串哈希

[ABC331F] Palindrome Query

#include <bits/stdc++.h>
using namespace std;
#define endl "\n"
#define int long long
typedef long long ll;

const int base = 131;
const int p1 = 1222827239;
const int N = 1e6 + 100;

int n, q, pn[N];
string s;

struct node {
    int lsum, rsum, len;
    node() {lsum = rsum = 0;}
} Seg[N * 4];

node operator + (const node &l, const node &r) {
    node ans;
    ans.lsum = (l.lsum + pn[l.len] * r.lsum % p1) % p1;
    ans.rsum = (r.rsum + pn[r.len] * l.rsum % p1) % p1;
    ans.len = l.len + r.len;
    return ans;
}

void pushup(int id) {
    Seg[id] = Seg[id * 2] + Seg[id * 2 + 1];
}

void build(int id, int l, int r) {
    Seg[id].len = r - l + 1;
    if (l == r) {
        Seg[id].lsum = Seg[id].rsum = s[l];
        return;
    }
    int mid = l + r >> 1;
    build(id * 2, l, mid); build(id * 2 + 1, mid + 1, r);
    pushup(id);
}    

void modify(int id, int l, int r, int pos, char c) {
    if (l == r) {
        Seg[id].lsum = Seg[id].rsum = c;
        return;
    }
    int mid = l + r >> 1;
    if (pos <= mid) modify(id * 2, l, mid, pos, c);
    else modify(id * 2 + 1, mid + 1, r, pos, c);
    pushup(id);
}

node query(int id, int l, int r, int x, int y) {
    if (x <= l && y >= r) return Seg[id];
    int mid = l + r >> 1;
    if (y <= mid) return query(id * 2, l, mid, x, y);
    if (x > mid) return query(id * 2 + 1, mid + 1, r, x, y);
    return query(id * 2, l, mid, x, y) + query(id * 2 + 1, mid + 1, r, x, y);
}

void solve() {
    cin >> n >> q >> s;
    
    s = " " + s;
    pn[0] = 1;
    for (int i = 1; i <= n; i++) pn[i] = pn[i - 1] * 1ll * base % p1;

    build(1, 1, n);

    while (q--) {
        int op; cin >> op;
        if (op == 1) {
            int pos; cin >> pos;
            char c; cin >> c;
            modify(1, 1, n, pos, c);
        } else {
            int l, r; cin >> l >> r;
            node ans = query(1, 1, n, l, r);
            if (ans.lsum == ans.rsum) cout << "Yes" << endl;
            else cout << "No" << endl;            
        }
    }
}    

signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);

    // int T = 1; cin >> T;
    // while(T--) solve();
    solve();

    return 0;    
}

 Kefa and Watch

#include <bits/stdc++.h>
using namespace std;
#define endl "\n"
#define int long long
typedef long long ll;

const int N = 1e6 + 100;
const int mod = 1222827239;
const int base = 131;

int n, m, k, pn[N], pre[N];
string s;

struct node {
    int sum, tag, len;
} Seg[N * 4];

void settag(int id, int v) {
    // cout << Seg[id].len << endl;
    Seg[id].sum = pre[Seg[id].len - 1] % mod * v % mod;
    Seg[id].tag = v;
}

void pushup(int id) {
    Seg[id].sum = (Seg[id * 2].sum + pn[Seg[id * 2].len] * Seg[id * 2 + 1].sum % mod) % mod;
}

void pushdown(int id) {
    if (Seg[id].tag) {
        settag(id * 2, Seg[id].tag);
        settag(id * 2 + 1, Seg[id].tag);
        Seg[id].tag = 0;
    }
}

void build(int id, int l, int r) {
    Seg[id].len = r - l + 1;
    Seg[id].tag = 0;
    if (l == r) {
        Seg[id].sum = s[l];
        return;
    }
    int mid = l + r >> 1;
    build(id * 2, l, mid); build(id * 2 + 1, mid + 1, r);
    pushup(id);
}

void modify(int id, int l, int r, int x, int y, char c) {
    if (x <= l && y >= r) {
        settag(id, c);
        return;
    }
    pushdown(id);
    int mid = l + r >> 1;
    if (x <= mid) modify(id * 2, l, mid, x, y, c);
    if (y > mid) modify(id * 2 + 1, mid + 1, r, x, y, c);
    pushup(id);
}

int query(int id, int l, int r, int x, int y) {
    if (x <= l && y >= r) return Seg[id].sum;
    pushdown(id);
    int mid = l + r >> 1;
    if (y <= mid) return query(id * 2, l, mid, x, y);
    if (x > mid) return query(id * 2 + 1, mid + 1, r, x, y);
    int ls = query(id * 2, l, mid, x, y), rs = query(id * 2 + 1, mid + 1, r, x, y), ans;
    ans = (ls + rs * pn[mid - max(l, x) + 1] % mod) % mod;
    return ans;
}

void solve() {
    cin >> n >> m >> k >> s;
    s = " " + s;

    build(1, 1, n);

    for (int i = 1; i <= m + k; i++) {
        int op, l, r; cin >> op >> l >> r;
        if (op == 1) {
            char d; cin >> d;
            modify(1, 1, n, l, r, d);
        } else {
            int d; cin >> d;
            if (d == r - l + 1) {
                cout << "YES" << endl;
                continue;
            }
            int v1 = query(1, 1, n, l, r - d) % mod;
            int v2 = query(1, 1, n, l + d, r) % mod;
            cout << (v1 == v2 ? "YES" : "NO") << endl;            
        }
    }    
}    

signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);

    // int T = 1; cin >> T;
    // while(T--) solve();
    pre[0] = pn[0] = 1;
    for (int i = 1; i <= N - 100; i++) pn[i] = pn[i - 1] * 1ll * base % mod, pre[i] = (pre[i - 1] + pn[i]) % mod;

    solve();

    return 0;    
}

 P2757 [国家集训队] 等差子序列

参考这位的P2757 [国家集训队]等差子序列 - GsjzTle思路

#include <bits/stdc++.h>
using namespace std;
#define endl "\n"
#define int long long
typedef long long ll;

const int N = 3e5 + 100;
const int mod = 1222827239;
const int base = 131;

int pn[N];

struct node {
    int lsum, rsum, len;
} Seg[N * 4];

void pushup(int id) {
    Seg[id].lsum = (Seg[id * 2].lsum + pn[Seg[id * 2].len] * Seg[id * 2 + 1].lsum % mod) % mod;
    Seg[id].rsum = (Seg[id * 2 + 1].rsum + pn[Seg[id * 2 + 1].len] * Seg[id * 2].rsum % mod) % mod;
}

void build(int id, int l, int r) {
    Seg[id].len = r - l + 1;
    if (l == r) {
        Seg[id].lsum = Seg[id].rsum = 0;
        return;
    }
    int mid = l + r >> 1;
    build(id * 2, l, mid); build(id * 2 + 1, mid + 1, r);
    pushup(id);
}

void modify(int id, int l, int r, int pos, int v) {
    if (l == r) {
        Seg[id].lsum = Seg[id].rsum = v;
        return;
    }
    int mid = l + r >> 1;
    if (pos <= mid) modify(id * 2, l, mid, pos, v);
    else modify(id * 2 + 1, mid + 1, r, pos, v);
    pushup(id);
}

int query(int id, int l, int r, int x, int y, int tag) {
    if (x <= l && y >= r) {
        if (tag) return Seg[id].lsum;
        else return Seg[id].rsum;
    }
    int mid = l + r >> 1;
    if (y <= mid) return query(id * 2, l, mid, x, y, tag);
    if (x > mid) return query(id * 2 + 1, mid + 1, r, x, y, tag);
    int ls = query(id * 2, l, mid, x, y, tag), rs = query(id * 2 + 1, mid + 1, r, x, y, tag), ans;
    //-----------------------------
    // 一定要这样写
    // pn[mid - max(x, l) + 1]
    // pn[min(y, r) - mid]
    //-----------------------------
    if (tag) ans = (ls + pn[mid - max(x, l) + 1] * rs % mod) % mod;
    else ans = (rs + pn[min(y, r) - mid] * ls % mod) % mod;
    return ans;
}

void solve() {
    int n; cin >> n;

    build(1, 1, n);

    bool ok = false;
    for (int i = 1; i <= n; i++) {
        int x; cin >> x;
        int len = min(x, n - x + 1);
        modify(1, 1, n, x, 1);
        if (i == 1 || i == n) continue;
        int v1 = query(1, 1, n, x - len + 1, x, 0);
        int v2 = query(1, 1, n, x, x + len - 1, 1);
        if (v1 != v2) ok = true;
    }
    if (ok) cout << "Y" << endl;
    else cout << "N" << endl;
}    

signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);

    pn[0] = 1;
    for (int i = 1; i < N; i++) pn[i] = pn[i - 1] * base % mod;

    solve();
    // int T = 1; cin >> T;
    // while (T--) solve();

    return 0;    
}