Submission #203607

#	Time	Username	Problem	Language	Result	Execution time	Memory
203607		stefdasca	Kangaroo (CEOI16_kangaroo)	C++14	51 / 100	2084 ms	17784 KiB

kangaroo

#include<bits/stdc++.h>
#define mod 1000000007
using namespace std;
int n, a, b;
int add(int a, int b)
{
    int x = a+b;
    if(x >= mod)
        x -= mod;
    if(x < 0)
        x += mod;
    return x;
}
int dp[2][2][2002][2002];
int main()
{
    cin >> n >> a >> b;
    for(int i = 1; i <= n; ++i)
        if(i != a && i != b)
            dp[0][(a < i)][i - 1 - (a < i)][b - (a < b) - (i < b)] = 1;
    if(n == 2)
    {
        cout << 1;
        return 0;
    }
    int ans = 0;
    for(int sum = n-2; sum >= 1; --sum)
    {
        for(int i = 0; i <= sum; ++i)
            for(int pos = 1; pos <= sum; ++pos)
            {
                int smaller = i;
                int bigger = sum - i;
                if(!dp[0][0][smaller][pos] && !dp[0][1][smaller][pos])
                    continue;
               // cout << sum << '\n';
              //  cout << smaller << " " << bigger << " " << pos << '\n';
              //  cout << dp[0][smaller][bigger][pos] << " " << dp[1][smaller][bigger][pos] << '\n';
                if(sum == 1)
                {
                    if(smaller)
                        ans = add(ans, dp[0][1][smaller][1]);
                    else
                        ans = add(ans, dp[0][0][smaller][1]);
                }
                else
                    for(int relpos = 1; relpos <= sum; ++relpos)
                    {
                        if(pos == relpos)
                            continue;
                        if(relpos <= smaller)
                            dp[1][0][relpos - 1][pos - (relpos < pos)] = add(dp[1][0][relpos - 1][pos - (relpos < pos)],
                                                                                        dp[0][1][smaller][pos]);
                        else
                            dp[1][1][relpos - 1][pos - (relpos < pos)] = add(dp[1][1][relpos - 1][pos - (relpos < pos)],
                                                                                        dp[0][0][smaller][pos]);
                    }
            }
        for(int x = 0; x <= 1; ++x)
            for(int q = 0; q <= n; ++q)
                for(int p = 0; p <= n; ++p)
                    dp[0][x][q][p] = dp[1][x][q][p], dp[1][x][q][p] = 0;
    }
    cout << ans;
    return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:33:21: warning: unused variable 'bigger' [-Wunused-variable]
                 int bigger = sum - i;
                     ^~~~~~

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