Submission #43388

#	Time	Username	Problem	Language	Result	Execution time	Memory
43388		funcsr	Kangaroo (CEOI16_kangaroo)	C++14	36 / 100	2039 ms	32860 KiB

kangaroo

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <string>
#include <cstring>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cmath>
#include <iomanip>
#include <cassert>
#include <bitset>
using namespace std;

typedef pair<int, int> P;
#define rep(i, n) for (int i=0; i<(n); i++)
#define all(c) (c).begin(), (c).end()
#define uniq(c) c.erase(unique(all(c)), (c).end())
#define index(xs, x) (int)(lower_bound(all(xs), x) - xs.begin())
#define _1 first
#define _2 second
#define pb push_back
#define INF 1145141919
#define MOD 1000000007
inline void add(int &x, int v) { x += v; if (x >= MOD) x -= MOD; }

int dp0[2001][2001];
int T[2001][2001];
int dp1[2001][2001];
int solve(int N, int CS, int CF) {
  rep(j, N+1) rep(k, N+1) dp0[j][k] = 0;
  dp0[CS][CF-(CS<CF)] = 1;
  rep(i, N-2) {
    int n = N-1-i;
    rep(j, n+1) rep(k, n+1) dp1[j][k] = 0;
    rep(j, n+1) rep(k, n+1) T[j][k] = dp0[j][k];
    rep(j, n) rep(k, n+1) add(T[j+1][k], T[j][k]);
    if (i%2 == 0) {
      rep(k, n+1) {
        rep(x, n) {
          if (x == k) continue;
          //rep(j, x+1) add(dp1[x][k-(x<=k)], dp0[j][k]);
          add(dp1[x][k-(x<=k)], T[x][k]);
        }
      }
    }
    else {
      rep(k, n+1) {
        rep(x, n+1) {
          if (x == k) continue;
          //for (int j=x+1; j<=n; j++) add(dp1[x][k-(x<=k)], dp0[j][k]);
          add(dp1[x][k-(x<=k)], T[n][k]);
          add(dp1[x][k-(x<=k)], MOD-T[x][k]);
        }
      }
    }
    swap(dp0, dp1);
  }
  int s = 0;
  rep(j, 2) {
    rep(k, 2) {
      if ((N-2)%2 == 0) {
        if (j == 0 && k == 0) add(s, dp0[j][k]);
      }
      else {
        if (k <= j-1) add(s, dp0[j][k]);
      }
    }
  }
  return s;
}

signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  int N, CS, CF;
  cin >> N >> CS >> CF;
  CS--, CF--;
  int s = solve(N, CS, CF);
  CS = N-1-CS, CF = N-1-CF;
  add(s, solve(N, CS, CF));
  cout << s << "\n";
  return 0;
}

• Subtask 1: 6 / 6
• Subtask 2: 30 / 30
• Subtask 3: 0 / 15
• Subtask 4: 0 / 49