Submission #1032691

#	Time	Username	Problem	Language	Result	Execution time	Memory
1032691		Kerim	Boat (APIO16_boat)	C++17	100 / 100	1186 ms	1916 KiB

boat

#include <bits/stdc++.h>
using namespace std;
 
using ll = long long;
 
#define sz(v) (int)(v).size()
 
const int md = (int)1e9 + 7;
 
const int N = 505;
 
vector<int> fct(N), inv(N), inv_fct(N);
 
int pw(int x, int y) {
    int res = 1;
    while (y) {
        if (y & 1) res = (ll)res * x % md;
 
        x = (ll)x * x % md; y >>= 1;
    }
 
    return res;
}
 
int C(int n, int r) {
    int x = 1;
    for (int i = 1; i <= r; i++) x = (ll)x * (n - r + i) % md;
 
    return (ll)x * inv_fct[r] % md;
}
int rdp[N][N], p[N];
int rec(int x, int y, vector<int>&v){
	if (x < 0)
		return 0;
	if (y == 1)
		return (rec(x-1, y, v) + p[v[x] - 1]) % md;	
	int &ret = rdp[x][y];
	if (~ret)
		return ret;
	return ret = (rec(x-1, y, v) + rec(x-1, y-1, v)) % md;
}
int main() {
	// freopen("file.in", "r", stdin);
    ios::sync_with_stdio(false); cin.tie(nullptr);
 
    fct[0] = inv[0] = inv_fct[0] = 1;
    for (int i = 1; i < N; i++) {
        inv[i] = pw(i, md - 2);
        fct[i] = (ll)fct[i - 1] * i % md;
        inv_fct[i] = pw(fct[i], md - 2);
    }
 
    int n;
    cin >> n;
 
    map<int, vector<int>> m;
    vector<int> a(n + 1), b(n + 1);
    for (int i = 1; i <= n; i++) {
        cin >> a[i] >> b[i];
 
        m[a[i]].push_back(i);
        m[b[i] + 1].push_back(-i);
    }
 
    vector<int> mv;
    for (auto i : m) mv.push_back(i.first);
 
    set<int> s;
    vector<int> dp(n + 1);
    for (int ii = 0; ii + 1 < sz(mv); ii++) {
        for (auto j : m[mv[ii]]) {
            if (0 < j) s.insert(j);
            else s.erase(-j); 
        }
 
        int R = mv[ii + 1] - mv[ii];

        vector<int> v(s.begin(), s.end()), nw_dp = dp;
        
        vector<int> c(sz(v));
        for (int j = 1; j < c.size(); j++)
        	c[j] = C(R, j + 1);

        memset(rdp, -1, sizeof rdp);

        p[0] = 1;
        for (int j = 1; j <= n; j++) 
        	p[j] = (p[j - 1] + dp[j]) % md;

        for (int i = 0; i < sz(v); i++) {
 
            nw_dp[v[i]] = (dp[v[i]] + (ll)p[v[i] - 1] * R % md) % md;
 
            for (int j = 1; j <= min(i, R - 1); j++) {
                nw_dp[v[i]] = (nw_dp[v[i]] + (ll)rec(i-1, j, v) * c[j] % md) % md;

                // x = (ll)fct[j - 1] * inv_fct[j - 1] % md;
                // for (int k = i - j; k >= 0; k--) {
                //     if (k != i - j) x = ((ll)x * (i - k - 1) % md) * inv[i - k - j] % md;
 
                //     nw_dp[v[i]] = (nw_dp[v[i]] + ((ll)p[v[k] - 1] * x % md) * c % md) % md;
                // }
            }
        }
 
        dp = nw_dp;
    }
 
    int sm = 0;
    for (auto i : dp) sm = (sm + i) % md;
 
    cout << sm << '\n';
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:81:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   81 |         for (int j = 1; j < c.size(); j++)
      |                         ~~^~~~~~~~~~

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