제출 #393919

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
393919		KhaledFarhat	Kangaroo (CEOI16_kangaroo)	C++14	0 / 100	2 ms	332 KiB

kangaroo

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

const int MOD = 1000000007;

int Add(int x, int y) {
    return (x + y) % MOD;
}

void Increase(int& x, int y) {
    x = Add(x, y);
}

int Multiply(int x, int y) {
    return 1LL * x * y % MOD;
}

int main() {
    freopen("kangaroo.in", "r", stdin);
    freopen("kangaroo.out", "w", stdout);

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n, startPosition, finishPosition;
    cin >> n >> startPosition >> finishPosition;

    vector<vector<int>> ways(n + 2, vector<int>(n + 1));

    ways[1][1] = 1;

    for (int i = 1; i <= n; ++i) {
        for (int components = 1; components <= i; ++components) {
            if (ways[i][components] == 0) {
                continue;
            }

            if (i == startPosition || i == finishPosition) {
                Increase(ways[i + 1][components + 1], ways[i][components]); // open a new component on the side
                Increase(ways[i + 1][components], ways[i][components]); // append to the side
            }
            else {
                // create a new component
                int validPosition = (components + 1) - (i > startPosition) - (i > finishPosition);
                Increase(ways[i + 1][components + 1], Multiply(validPosition, ways[i][components]));

                // merge two component
                validPosition = components - 1;
                Increase(ways[i + 1][components - 1], Multiply(validPosition, ways[i][components]));
            }
        }
    }

    cout << ways[n + 1][1];

    return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:19:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   19 |     freopen("kangaroo.in", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:20:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   20 |     freopen("kangaroo.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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