Submission #880413

#TimeUsernameProblemLanguageResultExecution timeMemory
880413DAleksaMisspelling (JOI22_misspelling)C++17
100 / 100
1577 ms319428 KiB
#include <bits/stdc++.h>
 
using namespace std;
 
const int mod = 1e9 + 7;
 
int add(int x, int y) { x += y; return x >= mod ? x - mod : x; }
int sub(int x, int y) { x -= y; return x < 0 ? x + mod : x; }
void sadd(int& x, int y) { x = add(x, y); }
void ssub(int& x, int y) { x = sub(x, y); }
 
struct Fenwick {
    int n;
    vector<int> fenw;
    Fenwick() { }
    Fenwick(int _n) {
        n = _n;
        fenw.resize(n);
        for(int i = 0; i < n; i++) fenw[i] = 0;
    }
    void update(int x, int val) { x++; for(int i = x; i < n; i += (i & -i)) sadd(fenw[i], val); }
    int get(int r) {
        r++;
        int ans = 0;
        for(int i = r; i >= 1; i -= (i & -i)) sadd(ans, fenw[i]);
        return ans;
    }
    int get(int l, int r) {
        if(l > r) return 0;
        return sub(get(r), get(l - 1));
    }
};
 
const int N = 5e5 + 10, M = 26;
int n, m;
int a[N], b[N];
int dp[N][M][2];
int important[N][2];
int first[N];
int pref[N][M][2];
vector<Fenwick> fw(M);
vector<int> down[N], up[N];
set<int> s;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    for(int i = 0; i < m; i++) {
        cin >> a[i] >> b[i];
        if(a[i] < b[i]) down[b[i]].push_back(a[i]);
        else up[a[i]].push_back(b[i]);
    }
    for(int i = n; i >= 1; i--) {
        auto it = s.upper_bound(i);
        if(it == s.begin()) important[i][0] = 0;
        else {
            it--;
            important[i][0] = *it;
        }
        for(int j : down[i]) s.insert(j);
    }
    s.clear();
    for(int i = n; i >= 1; i--) {
        auto it = s.upper_bound(i);
        if(it == s.begin()) important[i][1] = 0;
        else {
            it--;
            important[i][1] = *it;
        }
        for(int j : up[i]) s.insert(j);
    }
    for(int i = 1; i <= n; i++) {
        if(important[i][0] > important[i][1]) first[i] = 1;
        else {
            first[i] = 2;
            swap(important[i][0], important[i][1]);
        }
    }
    for(int i = 0; i < M; i++) fw[i] = Fenwick(n + 2);
    for(int c = 0; c < M; c++) {
        dp[0][c][0] = dp[0][c][1] = 1;
        fw[c].update(0, 1);
    }
    // for(int i = 1; i <= n; i++) cout << i << ": " << important[i][0] << " " << important[i][1] << " " << first[i] << "\n";
    for(int i = 1; i <= n; i++) {
        for(int c = 0; c < M; c++) {
            dp[i][c][0] = fw[c].get(important[i][0], i - 1);
            dp[i][c][1] = fw[c].get(important[i][1], important[i][0] - 1);
//            if(important[i][0] == 0) sadd(dp[i][c][0], 1);
//            if(important[i][1] == 0 && important[i][0] > 0) sadd(dp[i][c][1], 1);
        }
        pref[i][0][0] = dp[i][0][0];
        pref[i][0][1] = dp[i][0][1];
        for(int c = 1; c < M; c++) pref[i][c][0] = add(pref[i][c - 1][0], dp[i][c][0]);
        for(int c = 1; c < M; c++) pref[i][c][1] = add(pref[i][c - 1][1], dp[i][c][1]);
        for(int nwc = 0; nwc < M; nwc++) {
            fw[nwc].update(i, add(sub(pref[i][M - 1][0], pref[i][nwc][0]), (nwc > 0 ? pref[i][nwc - 1][0] : 0)));
            if(first[i] == 1) fw[nwc].update(i, sub(pref[i][M - 1][1], pref[i][nwc][1]));
            else if(first[i] == 2 && nwc > 0) fw[nwc].update(i, pref[i][nwc - 1][1]);
        }
    }
    // for(int i = 1; i <= n; i++) {
    //     for(int j = 0; j < M; j++) cout << dp[i][j][0] + dp[i][j][1] << " ";
    //     cout << "\n";
    // }
    int ans = 0;
    for(int c = 0; c < M; c++) {
        sadd(ans, dp[n][c][0]);
        sadd(ans, dp[n][c][1]);
    }
    cout << ans;
    return 0;
}
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