Submission #698867

#	Time	Username	Problem	Language	Result	Execution time	Memory
698867		dattranxxx	Kangaroo (CEOI16_kangaroo)	C++11	6 / 100	2 ms	3796 KiB

kangaroo

#include<bits/stdc++.h>
using namespace std;
using ll = long long;

const int N = 505, M = 1e9 + 7;
int A[N][N][N], D[N][N][N];

void add(int& x, int y) { x += y; if (x >= M) x -= M; }
void sub(int& x, int y) { x -= y; if (x < 0) x += M; }
int sum(int x, int y) { x += y; if (x >= M) x -= M; return x; }
int dif(int x, int y) { x -= y; if (x < 0) x += M; return x; }

int n, s, t;

int main() {
  cin.tie(0)->sync_with_stdio(0); cout.tie(0);
  cin >> n >> s >> t; 
  if (s > t) swap(s, t);
  
  A[2][1][2] = D[2][2][1] = 1;
  for (int i = 3; i <= n; ++i) {
    for (int s = 1; s <= i; ++s) {
      for (int t = i; t; --t) {
        
        if (s == t) continue;
        if (s > t) {
          A[i][s][t] = A[i][t][s];
          D[i][s][t] = D[i][t][s];
          continue;
        }
        
        if (s == 1) {
          for (int j = s; j <= i - 1; ++j) {
            add(A[i][s][t], D[i - 1][j][t - 1]);
          }
          
          for (int j = 1; j <= s - 1; ++j) {
            add(D[i][s][t], A[i - 1][j][t - 1]);
          }
        } else {
          A[i][s][t] = dif(A[i][s - 1][t], D[i - 1][s - 1][t - 1]);
          D[i][s][t] = sum(D[i][s - 1][t], A[i - 1][s - 1][t - 1]);
        }
        
        // cerr << i << ' ' << s << ' ' << t << ' ' << A[i][s][t] << ' ' << D[i][s][t] << '\n';
        
      }
    }
  }
  
  cout << sum(A[n][s][t], D[n][s][t]);

	return 0;
}

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