Submission #1054588

#	Time	Username	Problem	Language	Result	Execution time	Memory
1054588		anango	Trains (BOI24_trains)	C++17	100 / 100	108 ms	13828 KiB

Main

#include <bits/stdc++.h>
#define int long long
using namespace std;

const int MOD = 1000000007;
const int K = 100;

int debug = 0;

signed main() {
    #ifndef ONLINE_JUDGE
        // for getting input from input.txt
        //freopen("input.txt", "r", stdin);
        // for writing output to output.txt
        //freopen("output.txt", "w", stdout);
    #endif
    #ifdef ONLINE_JUDGE
    	ios_base::sync_with_stdio(false);
    	cin.tie(NULL);
    #endif //fast IO
    int n; cin >> n;
    int dp[n]; //number of journeys ending at the ith city
    vector<int> D(n); vector<int> X(n);
    for (int i=0; i<n; i++) {
        cin >> D[i];
        cin >> X[i];
    }
    int prop[K][K];
    for (int i=0; i<n; i++) {
        dp[i] = 0;
    }
    for (int i=0; i<K; i++) {
        for (int j=0; j<K; j++) {
            prop[i][j] = 0;
        }
    }
    vector<vector<vector<int>>> req_updates(n); //update values are in form {d_i, residue, value}
    dp[0] = 1;
    for (int i=0; i<n; i++) {
        for (int j=1; j<K; j++) {
            if (debug) cout << "adding " << i <<" " << j <<" " << i%j <<" " << prop[j][i%j] << endl;
            dp[i]+=prop[j][i%j];
            dp[i]%=MOD;
        }
        int d = D[i];
        if (d==0) {
            for (auto update:req_updates[i]) {
                int di,residue,value;
                di=update[0]; residue=update[1]; value=update[2];
                if (debug) cout << "removed " << i <<" " << di <<" " << residue <<" " << value << " " << update[3] << endl;
                prop[di][residue]-=value; prop[di][residue]%=MOD; prop[di][residue]+=MOD; prop[di][residue]%=MOD;
            }
            continue;
        }
        int x = X[i];
        int end = i+x*d;
        end = min(end,((n-1-(i%d))/d)*d+i%d);
        //if (debug) cout << i <<" " << d <<" " << x <<" " << end << " " << ((n-1-(i%d))/d)*d+i%d << endl;
        int ans = 0;
        if (d<K) {
            prop[d][i%d]+=dp[i]; prop[d][i%d]%=MOD;
            req_updates[end].push_back({d,i%d,dp[i],i});
            if (debug) cout << "added update " << i <<" " << end <<" " << d <<" " << i%d <<" " << dp[i] << endl;
            if (debug) cout << "sizing " << req_updates[end].size() << endl;
        }
        else {
            for (int j=i+d; j<=end; j+=d) {
                dp[j]+=dp[i]; dp[j]%=MOD;
            }
        }
        for (auto update:req_updates[i]) {
            int di,residue,value;
            di=update[0]; residue=update[1]; value=update[2];
            if (debug) cout << "removed " << i <<" " << di <<" " << residue <<" " << value << " " << update[3] << endl;
            prop[di][residue]-=value; prop[di][residue]%=MOD; prop[di][residue]+=MOD; prop[di][residue]%=MOD;
        }
    }
    int su = 0;
    for (int i=0; i<n; i++) {
        su+=dp[i]; su%=MOD;
        if (debug) cout << dp[i] <<" ";
    }
    if (debug) cout << endl;
    cout << su << endl;
    
    
    
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:59:13: warning: unused variable 'ans' [-Wunused-variable]
   59 |         int ans = 0;
      |             ^~~

• Subtask 1: 8 / 8
• Subtask 2: 13 / 13
• Subtask 3: 16 / 16
• Subtask 4: 34 / 34
• Subtask 5: 29 / 29