Submission #1073922

#	Time	Username	Problem	Language	Result	Execution time	Memory
1073922		RiverFlow	Boat (APIO16_boat)	C++14	31 / 100	360 ms	4268 KiB

boat

#include <bits/stdc++.h>

#define nl "\n"
#define no "NO"
#define yes "YES"
#define fi first
#define se second
#define vec vector
#define task "main"
#define _mp make_pair
#define ii pair<int, int>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define evoid(val) return void(std::cout << val)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FOD(i, b, a) for(int i = (b); i >= (a); --i)
#define unq(x) sort(all(x)); x.resize(unique(all(x)) - x.begin())

using namespace std;

template<typename U, typename V> bool maxi(U &a, V b) {
    if (a < b) { a = b; return 1; } return 0;
}
template<typename U, typename V> bool mini(U &a, V b) {
    if (a > b) { a = b; return 1; } return 0;
}

const int N = (int)500 + 9;
const int mod = (int)1e9 + 7;

void prepare(); void main_code();

int main() {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    const bool MULTITEST = 0; prepare();
    int num_test = 1; if (MULTITEST) cin >> num_test;
    while (num_test--) { main_code(); }
}

void prepare() {};

int n, a[N], b[N];

namespace SUB1 {
int dp[N][N];
void add(int &a, int b) {
    a += b;
    if (a >= mod) a -= mod;
}
void sol() {
    dp[0][0] = 1;
    a[0] = b[0] = 0;
    FOR(i, 0, n - 1) FOR(j, 0, i) if (dp[i][j]) {
        add(dp[i + 1][j], dp[i][j]);
        if (b[i + 1] > b[j])
            add(dp[i + 1][i + 1], dp[i][j]);
    }
    int res = 0;
    FOR(i, 1, n) add(res, dp[n][i]);
    cout << res;
}
};

namespace SUB2 {
int S[N];
vector<int> dp[N];
void add(int &a, int b) {
    a += b;
    if (a >= mod) a -= mod;
}

void sol() {
    int res = 0;
    for(int i = 1; i <= n; ++i) {
        int os = 1;
        int L = b[i] - a[i] + 1;
        S[i] = L;
        dp[i].resize(L);
        for(int j = 1; j < i; ++j) {
            if (a[i] > b[j]) {
                add(os, dp[j][S[j] - 1]);
            } else if (max(a[i], a[j]) <= min(b[i], b[j])) {
                if (a[i] >= a[j]) {
                    for(int x = 0; x < L; ++x) {
                        if (x + a[i] - a[j] - 1 >= 0)
                            add(dp[i][x], dp[j][min(x + a[i] - a[j] - 1, S[j] - 1)]);
                    }
                } else {
                    for(int x = a[j] + 1; x <= b[i]; ++x) {
                        add(dp[i][x - a[i]], dp[j][min(x - a[j] - 1, S[j] - 1)]);
                    }
                }
            }
        }
        for(int x = 0; x < L; ++x) {
            add(dp[i][x], os);
            if (x > 0) add(dp[i][x], dp[i][x - 1]);
        }
        add(res, dp[i][L - 1]);
    }
    cout << res;
}
};
void main_code() {
    cin >> n;
    long long sum = 0;
    for(int i = 1; i <= n; ++i) cin >> a[i] >> b[i], sum += b[i] - a[i] + 1;
    if (n <= 500 and sum == n) {
        return SUB1::sol(), void();
    }
    if (n <= 500 and sum <= (int)1e6 + 7) {
        return SUB2::sol(), void();
    }
}


/*     Let the river flows naturally     */

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:36:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
boat.cpp:37:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 22 / 22
• Subtask 3: 0 / 27
• Subtask 4: 0 / 42