2023.2.16 普及组

[Yapink]

第一题：约数问题，看了数学公式推导才明白这么简单

#include <iostream>

using namespace std;

const int N = 100010;

int main()
{
	int n;
	scanf("%d", &n);
	
	int res = 0;
	for (int i = 1; i <= n; i ++ ) res += n / i;
	printf("%d\n", res);
	
	return 0;
}

 第二题：贪心模板题

#include <iostream>
#include <algorithm>

using namespace std;

typedef pair<int, int> PII;

const int N = 50010;

int n, w, s;
PII cow[N];

int main()
{
	scanf("%d", &n);
	for (int i = 0; i < n; i ++ ) 
	{
		int w, s;
		cin >> w >> s;
		cow[i] = {w + s, w};
	}

	sort(cow, cow + n);
	
	int res = -2e9, sum = 0;
	for (int i = 0; i < n; i ++ ) 
	{
		int w = cow[i].second, s = cow[i].first - cow[i].second;
		res = max(res, sum - s);
		sum += w;
	}
	
	cout << res << endl;
	return 0;
}

 第三题：01背包多一重限制，只是多一重循环，多一维数组

#include <iostream>

using namespace std;

const int N = 55, T = 410;

int n, V, M;
int f[T][T];

int main()
{
	scanf("%d%d%d", &V, &M, &n);
	
	for (int i = 1; i <= n; i ++ ) 
	{
		int v, m, k;
		cin >> v >> m >> k;	
		for (int j = V; j >= v; j -- )
			for (int u = M; u >= m; u -- )
				f[j][u] = max(f[j][u], f[j - v][u - m] + k);
	}	
	
	cout << f[V][M] << endl;
	return 0;
}