Submission #742023

#	Time	Username	Problem	Language	Result	Execution time	Memory
742023		vjudge1	Boat (APIO16_boat)	C++17	0 / 100	1308 ms	11396 KiB

boat

#include <algorithm>
#include <iostream>
#include <iomanip>
#include <bitset>
#include <cmath>
#include <queue>
#include <map>
#include <set>

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define ent "\n"

const int maxn = 5e2 + 100;
const ll INF = (1ll<<61);
const int MOD = 1e9 + 7;
const int inf = (1<<30);
const int maxl = 20;
const int P = 31;

int n;
int a[maxn];
int b[maxn];
ll dp[550][1010];
int cal[maxn];
ll f[maxn * 2][maxn];
ll br[maxn];
ll cnk[maxn][maxn];
vector<int> v;

ll binpow(ll a, ll b){
    if(!b) return 1;
    ll num = binpow(a, b >> 1);
    num = num * num % MOD;
    if(b & 1) num = num * a % MOD;
    return num;
}

int c(int n, int k){
    if(k > n) return 0;
    ll ans = 1;
    for(int i = n - k + 1; i <= n; i++){
        ans = (ans * i) % MOD;
    }
    for(int i = 1; i <= k; i++){
        ans = (ans * br[i]) % MOD;
    }
    return ans;
}

bool ok(int i, int j){
    return v[j] >= a[i] && v[j+1] - 1 <= b[i];
}

void test(){
    cin >> n;
    for(int i = 1; i <= n; i++){
        cin >> a[i] >> b[i];
        v.push_back(a[i]);
        v.push_back(b[i] + 1);
        br[i] = binpow(i, MOD - 2);
    }
    v.push_back(1e9 + 1);
    sort(v.begin(), v.end());
    v.resize(unique(v.begin(), v.end()) - v.begin());
    int ans = 0;
    cnk[0][0] = 1;
    for(int i = 1; i <= n; i++){
        for(int j = 0; j <= i; j++){
            cnk[i][j] = cnk[i-1][j];
            if(j) cnk[i][j] = (cnk[i][j] + cnk[i-1][j-1]) % MOD;
        }
    }
    for(int i = 0; i < v.size() - 1; i++){
        for(int j = 0; j <= n; j++){
            f[i][j] = c(v[i+1] - v[i], j);
        }
        for(int j = n - 1; j > 0; j--){
            for(int k = j + 1; k <= n; k++){
                f[i][k] = (f[i][k] + 1ll * cnk[k-1][j-1] * f[i][j]) % MOD;
            }
        }
    }
    for(int i = 1; i <= n; i++){
        for(int k = i - 1; k > 0; k--){
            for(int j = 0; j < v.size() - 1; j++){
                if(ok(k+1, j)) cal[j]++;
                if(j) dp[i][j] = (dp[i][j] + 1ll * dp[k][j-1] * f[j][cal[j]]) % MOD;
            }
        }
        for(int j = 0; j < v.size() - 1; j++){
            dp[i][j] += f[j][cal[j]];
            if(!ok(i, j)) dp[i][j] = 0;
            ans = (ans + dp[i][j]) % MOD;
            if(j) dp[i][j] = (dp[i][j] + dp[i][j-1]) % MOD;
        }
    }
    cout << ans << ent;
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    int t; t = 1;
    while(t--) test();
}

Compilation message (stderr)

boat.cpp: In function 'void test()':
boat.cpp:76:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   76 |     for(int i = 0; i < v.size() - 1; i++){
      |                    ~~^~~~~~~~~~~~~~
boat.cpp:88:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   88 |             for(int j = 0; j < v.size() - 1; j++){
      |                            ~~^~~~~~~~~~~~~~
boat.cpp:93:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   93 |         for(int j = 0; j < v.size() - 1; j++){
      |                        ~~^~~~~~~~~~~~~~

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