Submission #116520

#	Time	Username	Problem	Language	Result	Execution time	Memory
116520		JohnTitor	Kangaroo (CEOI16_kangaroo)	C++11	100 / 100	17 ms	508 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
#define FOR(i, j, k) for(int i=(j); i<=(k); i++)
#define FFOR(i, j, k) for(int i=(j); i<(k); i++)
#define DFOR(i, j, k) for(int i=(j); i>=(k); i--)
#define bug(x) cerr<<#x<<" = "<<(x)<<'\n'
#define pb push_back
#define mp make_pair
#define bit(s, i) (((s)>>(i))&1LL)
#define mask(i) ((1LL<<(i)))
#define builtin_popcount __builtin_popcountll
#define __builtin_popcount __builtin_popcountll
using ll=long long; using ld=long double;
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count()); const ld pi=acos(0)*2;
template <typename T> inline void read(T &x){char c; bool nega=0; while((!isdigit(c=getchar()))&&(c!='-')); if(c=='-'){nega=1; c=getchar();} x=c-48; while(isdigit(c=getchar())) x=x*10+c-48; if(nega) x=-x;}
template <typename T> inline void writep(T x){if(x>9) writep(x/10); putchar(x%10+48);}
template <typename T> inline void write(T x){if(x<0){ putchar('-'); x=-x;} writep(x);}
template <typename T> inline void writeln(T x){write(x); putchar('\n');}
#define taskname "Kangaroo"
int n;
ll f[2002];
ll g[2002];
int s, e;
const ll base=1000000007;
int main(){
    #ifdef Aria
        if(fopen(taskname".in", "r"))
            freopen(taskname".in", "r", stdin);
    #endif // Aria
    f[1]=1;
    read(n);
    read(s);
    read(e);
    DFOR(i, n-1, 1){
        FOR(j, 1, n) g[j]=0;
        if(i==s||i==e){
            FOR(j, 1, n) if(f[j]) g[j]=(g[j]+f[j])%base;
            FOR(j, 1, n) if(f[j]) g[j+1]=(g[j+1]+f[j])%base;
        }
        else{
            FOR(j, 1, n) if(f[j]){
                g[j-1]=(g[j-1]+f[j]*(j-1))%base;
                g[j+1]=(g[j+1]+f[j]*(j-1))%base;
                if(i>e) g[j+1]=(g[j+1]+f[j])%base;
                if(i>s) g[j+1]=(g[j+1]+f[j])%base;
            }
        }
        FOR(j, 1, n) f[j]=g[j];
//        bug(i);
//        FOR(i, 1, n) cerr<<f[i]<<" \n"[i==n];
    }
    writeln(f[1]);
}

• Subtask 1: 6 / 6
• Subtask 2: 30 / 30
• Subtask 3: 15 / 15
• Subtask 4: 49 / 49