Submission #40744

#TimeUsernameProblemLanguageResultExecution timeMemory
40744ssnsarang2023Boat (APIO16_boat)C++14
9 / 100
389 ms2840 KiB
#include <bits/stdc++.h> using namespace std; typedef long long ll; typedef unsigned long long ull; typedef pair<int, int> ii; #define SZ(x) ((int)x.size()) const int mod = (int)1e9+7; const int N = 505; int n, f[N], g[N], ftmp[N], gtmp[N], a[N], b[N], inv[N], tmp[N], m; int choose[N][N], nCk[N], nCk2[N], choose1[N][N], choose2[N][N]; vector<int> c; int mul(int x, int y) { x %= mod, y %= mod; if (x < 0) x += mod; if (y < 0) y += mod; ll re = (ll)x * (ll)y % (ll)mod; return (int)re; } void add(int &x, int y) { x += y, x %= mod; if (x < 0) x += mod; } int fast_pw(int x, int y) { if (y == 1) return x % mod; if (y == 0) return 1; int t = fast_pw(x, y >> 1); t = mul(t, t); if (y & 1) t = mul(t, x); return t; } int main() { scanf("%d", &n); for (int i = 1; i <= n; ++i) { scanf("%d%d", &a[i], &b[i]); c.push_back(a[i]); c.push_back(b[i]); } sort(c.begin(), c.end()); c.resize(distance(c.begin(), unique(c.begin(), c.end()))); for (int i = 0; i <= n; ++i) choose[i][i] = choose[i][0] = 1; inv[0] = f[0] = g[0] = 1; for (int i = 1; i <= n; ++i) { for (int j = 1; j < i; ++j) choose[i][j] = (choose[i - 1][j - 1] + choose[i - 1][j]) % mod; inv[i] = mul(inv[i - 1], fast_pw(i, mod - 2)); g[i] = 1; } int sz = SZ(c); c.push_back(n); for (int i = 0; i < sz; ++i) { m = 0; int total = c[i + 1] - c[i], tmp_mul1 = 1, tmp_mul2 = 1; for (int j = 1; j <= n; ++j) { if (b[j] == c[i]) ftmp[j] = gtmp[j] = g[j - 1]; else if (a[j] <= c[i] && c[i] <= b[j]) tmp[++m] = j; if (total - j + 1 > 0) { tmp_mul1 = mul(tmp_mul1, total - j + 1); nCk[j] = mul(tmp_mul1, inv[j]); } if (total - j > 0) { tmp_mul2 = mul(tmp_mul2, total - j); nCk2[j] = mul(tmp_mul2, inv[j]); } } if (m > 0) { for (int j = 1; j <= n; ++j) add(gtmp[j], gtmp[j - 1]); for (int j = 0; j <= m - 2; ++j) { int lmt = min(j, total - 2); for (int k = 0; k <= lmt; ++k) { choose1[j][k] = mul(choose[j][k], nCk[k + 2]); choose2[j][k] = mul(choose[j][k], nCk2[k + 2]); add(choose1[j][k], choose1[j][k - 1]); add(choose2[j][k], choose2[j][k - 1]); } } for (int j = m; j > 0; --j) { int id = tmp[j]; add(ftmp[id], mul(nCk[1], g[id - 1])); if (total > 1) { for (int k = j - 1; k > 0; --k) { int mid = j - k - 1, id2 = tmp[k]; add(ftmp[id], mul(g[id2 - 1], choose1[mid][min(mid, total - 2)])); if (total > 2) add(ftmp[id], mul(gtmp[id2 - 1], choose2[mid][min(mid, total - 3)])); } } } } g[0] = 1; for (int i = 1; i <= n; ++i) { add(f[i], ftmp[i]); g[i] = (g[i - 1] + f[i]) % mod; ftmp[i] = gtmp[i] = 0; } } printf("%d", (g[n] - 1 + mod) % mod); return 0; }

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:40:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
                 ^
boat.cpp:42:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &a[i], &b[i]);
                              ^
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