Submission #27789

#TimeUsernameProblemLanguageResultExecution timeMemory
27789sampritiBoat (APIO16_boat)C++14
9 / 100
2000 ms6144 KiB
#include <iostream> #include <iomanip> #include <algorithm> #include <vector> #include <cstring> #define MOD 1000000007LL using namespace std; int A[500], B[500]; vector<int> T; int start_i[500], end_i[500]; long long dp[501][1000 + 10]; long long modpow(long long base, long long exp) { long long res = 1; while(exp) { if(exp & 1) res = (res * base) % MOD; base = (base * base) % MOD; exp >>= 1; } return res; } int main() { ios::sync_with_stdio(false); cin.tie(0); int N; cin >> N; for(int i = 0; i < N; i++) { cin >> A[i] >> B[i]; T.push_back(A[i]); T.push_back(B[i] + 1); } sort(T.begin(), T.end()); T.resize(unique(T.begin(), T.end()) - T.begin()); int M = T.size(); for(int i = 0; i < N; i++) { start_i[i] = lower_bound(T.begin(), T.end(), A[i]) - T.begin(); end_i[i] = upper_bound(T.begin(), T.end(), B[i]) - T.begin(); } for(int j = 0; j < M; j++) dp[N][j] = 1; for(int i = N - 1; i >= 0; i--) { for(int j = start_i[i]; j < end_i[i]; j++) { int len = T[j + 1] - T[j]; dp[i][j] += len * dp[i + 1][j + 1]; dp[i][j] %= MOD; int cnt = 1; long long curr = len - 1; for(int k = i + 1; k < N; k++) { if(start_i[k] <= j && j < end_i[k]) { cnt++; curr = (curr * (len + cnt - 2)) % MOD; curr = (curr * modpow(cnt, MOD - 2)) % MOD; dp[i][j] += curr * dp[k + 1][j + 1]; dp[i][j] %= MOD; } } } for(int j = M - 1; j >= 0; j--) { dp[i][j] += dp[i][j + 1]; } for(int j = M - 1; j >= 0; j--) { dp[i][j] += dp[i + 1][j]; } } cout << (dp[0][0] - 1 + MOD) % MOD << endl; // for(int j = 0; j < M; j++) cout << setw(5) << T[j]; // cout << endl << endl; // for(int i = 0; i < N; i++) { // for(int j = 0; j < M; j++) { // cout << setw(5) << dp[i][j]; // } // cout << endl; // } }
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