上海市计算机学会月赛2021年3月乙组

    #include <iostream>
    using namespace std;
    
    void f(int x) {
    	if (x == 0) return;
    	
    	if (x%3 == 2) f(x/3 + 1), cout << 'z';
    	else if (x%3 == -2) f(x/3 - 1), cout << '1';
    	else if (x%3 == -1) f(x/3), cout << 'z';
    	else f(x/3), cout << x%3;
    }
    
    int main() {
    	int n;
    	cin >> n;
    
    	if (n == 0) cout << 0;
    	else f(n);
    
    	return 0;
    }

    #include <iostream>
    #include <cmath>
    #include <algorithm>
    using namespace std;
    
    long long a, b, c;
    int cnt, ans[10000];
    
    int main() {
    	for (int i = 0; i <= 31; i ++) {
    		a = pow(2, i);
    		for (int j = 0; j <= 20; j ++) {
    			b = pow(3, j);
    			if (a*b > 2e9) break;
    			for (int k = 0; k <= 15; k ++) {
    				c = pow(5, k);
    				if (a*b*c > 2e9) break;
    				ans[++cnt] = a*b*c;
    			}
    		}
    	}
    
    	sort(ans+1, ans+1+cnt);
    	
    	int n;
    	cin >> n;
    	cout << ans[n];
    
    	return 0;
    }

    #include <iostream>
    using namespace std;
    
    const int N = 1e5+10, MOD = 1e9+7;
    int n, a[N] = {1,2}, sum = 4;
    
    int main() {
    	cin >> n;
    	for (int i = 2; i <= n; i ++) {
    		a[i] = (sum + a[i-2] + 2) % MOD;
    		sum = (sum + a[i]) % MOD;
    		sum = (sum + a[i]) % MOD;
    	}
    	cout << a[n];
    
    	return 0;
    }

    #include <iostream>
    #include <cstring>
    using namespace std;
    
    const int N = 5100, M = 1e4 + 10;
    int n, m, w[N], c[N], f[M], g[M];
    
    int main() {
    	cin >> n >> m;
    	
    	int t = 0;
    	for (int i = 1; i <= n; i ++) cin >> w[i] >> c[i];
    
    	for (int i = 1; i <= n; i ++) {
    		for (int j = m; j >= w[i]; j --) {
    			f[j] = max(f[j], f[j-w[i]] + c[i]);
    			
    			g[j] = max(g[j], f[j-1] + c[i]);
    			g[j] = max(g[j], g[j-w[i]] + c[i]);
    //			cout << i << ' ' << j << ' ' << f[i][j] << ' ' << g[i][j] << endl;
    		}
    	}
    	
    	cout << 2 * g[m];
    
    	return 0;
    }