Submission #392126

#TimeUsernameProblemLanguageResultExecution timeMemory
392126soroushBoat (APIO16_boat)C++17
100 / 100
579 ms4428 KiB
//曇り空 のぞいた予感 #include <bits/stdc++.h> using namespace std; typedef long long ll; typedef long double ld; typedef pair<int , int> pii; mt19937 rng(chrono::steady_clock::now().time_since_epoch().count()); const int maxn = 1010; const ll mod = 1e9+7; #define pb push_back #define endl '\n' #define dokme(x) cout << x , exit(0) #define ms(x , y) memset(x , y , sizeof x) ll pw(ll a, ll b, ll md = mod){ll res = 1;while(b){if(b&1){res=(a*res)%md;}a=(a*a)%md;b>>=1;}return(res);} vector < int > vec; int n , m , inv[maxn]; int l[maxn] , r[maxn]; int dp[maxn][maxn*2]; int ans; int32_t main(){ ios::sync_with_stdio(false),cin.tie(0),cout.tie(0); for(int i = 1 ; i < maxn ; i ++)inv[i] = pw(i , mod - 2); cin >> n; for(int i = 1 ; i <= n ; i ++) cin >> l[i] >> r[i] , r[i]++ , vec.pb(l[i]) , vec.pb(r[i]); sort(vec.begin() , vec.end()); vec.resize(unique(vec.begin() , vec.end()) - vec.begin()); m = vec.size(); for(int i = 0 ; i < m ; i ++)dp[0][i] = 1; for(int i = 1 ; i <= n ; i ++) l[i] = lower_bound(vec.begin() , vec.end() , l[i])-vec.begin()+1, r[i] = lower_bound(vec.begin() , vec.end() , r[i])-vec.begin()+1; for(int i = 1 ; i <= n ; i ++){ for(int j = l[i] ; j < r[i] ; j ++){ ll C = vec[j]-vec[j-1]; ll x = vec[j]-vec[j-1], y = 1; for(int k = i-1 ; k >= 0 ; k --){ dp[i][j] = (dp[i][j] + (dp[k][j-1] * 1ll * C)%mod)%mod; if(l[k] <= j and j < r[k]){ x++ , ++y; C = (C * ((x * inv[y])%mod))%mod; } } } for(int j = 0 ; j < m ; j ++)dp[i][j] = (dp[i][j] + dp[i][j-1])%mod; ans = (ans + dp[i][m-1])%mod; } cout << ans; return(0); }
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