Submission #712579

#TimeUsernameProblemLanguageResultExecution timeMemory
712579GrindMachineMisspelling (JOI22_misspelling)C++17
100 / 100
1368 ms305788 KiB
// Om Namah Shivaya

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl

#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a, b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a, b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif

/*



*/

const int MOD = 1e9 + 7;
const int N = 5e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

ll dp[N][26], pref[N][26];

void solve(int test_case)
{
    ll n, m; cin >> n >> m;
    vector<array<ll, 3>> a(m);
    rep(i, m) {
        ll l, r; cin >> l >> r;
        ll t = 0;
        if (l > r) {
            swap(l, r);
            t = 1;
        }
        a[i] = {t, l, r - 1};
    }

    rep(ch, 26) {
        dp[1][ch] = 1;
        pref[1][ch] = 1;
    }

    vector<ll> enter[n + 5][2], leave[n + 5][2];

    rep(j, m) {
        auto [t, l, r] = a[j];
        enter[l + 1][t].pb(l);
        leave[r + 2][t].pb(l);
    }

    multiset<ll> st1, st2;
    st1.insert(0);
    st2.insert(0);

    for (int i = 2; i <= n; ++i) {
        trav(l, enter[i][0]) {
            st1.insert(l);
        }
        trav(l, enter[i][1]) {
            st2.insert(l);
        }

        trav(l, leave[i][0]) {
            st1.erase(st1.find(l));
        }
        trav(l, leave[i][1]) {
            st2.erase(st2.find(l));
        }

        ll mx_les = *st1.rbegin();
        ll mx_mor = *st2.rbegin();

        /*

        ll mx_les = 0, mx_mor = 0;

        rep(j, m) {
            auto [t, l, r] = a[j];
            if (l <= i - 1 and r >= i - 1) {
                if (t == 0) {
                    amax(mx_les, l);
                }
                else {
                    amax(mx_mor, l);
                }
            }
        }

        */

        rep(ch1, 26) {
            auto &val = dp[i][ch1];
            rep(ch2, 26) {
                if (ch2 == ch1) {
                    // val += pref[i - 1][ch2];
                }
                else if (ch2 < ch1) {
                    val += pref[i - 1][ch2] - pref[mx_les][ch2];
                }
                else {
                    val += pref[i - 1][ch2] - pref[mx_mor][ch2];
                }
            }

            val = (val % MOD + MOD) % MOD;
        }

        rep(ch, 26) {
            pref[i][ch] = (pref[i - 1][ch] + dp[i][ch]) % MOD;
        }
    }

    ll ans = 0;
    rep(ch, 26) ans = (ans + pref[n][ch]) % MOD;

    cout << ans << endl;
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;

    rep1(i, t) {
        solve(i);
    }

    return 0;
}
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