Submission #532158

#	Time	Username	Problem	Language	Result	Execution time	Memory
532158		79brue	Boat (APIO16_boat)	C++14	9 / 100	11 ms	564 KiB

boat

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const ll MOD = 1000000007;

ll mpow(ll x, ll y){
    if(!y) return 1;
    if(y&1) return (mpow(x, y-1)*x)%MOD;
    ll tmp = mpow(x, y/2);
    return (tmp*tmp)%MOD;
}

int n;
int a[502], b[502];
map<int, int> idx;
vector<int> renumber;

ll DP[1002], DPsum[1002];
ll DP2[1002][1002];
ll modInv[1002];
ll ans;

int main(){
    scanf("%d", &n);
    for(int i=1; i<=n; i++){
        scanf("%d %d", &a[i], &b[i]);
        b[i]++;
        renumber.push_back(a[i]);
        renumber.push_back(b[i]);
    }
    sort(renumber.begin(), renumber.end());
    renumber.erase(unique(renumber.begin(), renumber.end()), renumber.end());
    for(int i=0; i<(int)renumber.size(); i++){
        idx[renumber[i]] = i;
    }

    for(int i=1; i<=1000; i++){
        modInv[i] = mpow(i, MOD-2);
    }

    DP[0] = 1;
    for(int i=1; i<(int)renumber.size(); i++){
        int s = renumber[i-1], e = renumber[i];
        DPsum[0] = 1;
        vector<int> tv;

        for(int j=1; j<=n; j++){
            DPsum[j] = (DPsum[j-1] + DP[j]) % MOD;
            if(a[j] <= s && e <= b[j]) tv.push_back(j);
        }

        for(int j=1; j<=(int)tv.size() && j<=e-s; j++){
            for(int k=j-1; k<(int)tv.size(); k++){
                if(j==1){
                    DP2[j][k] = DPsum[tv[k]-1]*(e-s);
                    if(k!=0) DP2[j][k] += DP2[j][k-1];
                    DP2[j][k]%=MOD;
                }
                else{
                    DP2[j][j] = ((DP2[j-1][k-1] * modInv[j]) % MOD) * ((e-s+1) - i) + DP2[j][k-1];
                    DP2[j][k]%=MOD;
                }
            }
        }

        for(int j=1; j<=(int)tv.size() && j<=e-s; j++){
            for(int k=j-1; k<(int)tv.size(); k++){
                int tmp = (DP2[j][k] - (k?DP2[j][k-1]:0) + MOD) % MOD;
                DP[tv[k]] += tmp;
                DP[tv[k]] %= MOD;
            }
        }
    }

    for(int i=1; i<=n; i++) ans = (ans + DP[i]) % MOD;
    printf("%lld", ans);
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:27:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   27 |     scanf("%d", &n);
      |     ~~~~~^~~~~~~~~~
boat.cpp:29:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   29 |         scanf("%d %d", &a[i], &b[i]);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 0 / 22
• Subtask 3: 0 / 27
• Subtask 4: 0 / 42