CP_mid2

a.cpp

#include <iostream>
#include <algorithm>
using namespace std;

unsigned long long int a[100001] = {}, n, s, t;

unsigned long long int f()
{
	sort(a + 1, a + n + 1);
	for(int i = 1; i <= n; ++i)
	{
		a[i] += a[i - 1];
	}
	return a[t] - a[s - 1];
}

int main(int argc, char const *argv[])
{
	int T;
	cin >> T;
	while(T--)
	{
		cin >> n >> s >> t;
		for(int i = 1; i <= n; ++i)
		{
			cin >> a[i];
		}
		cout << f() << endl;
	}
	return 0;
}

b.cpp

#include <iostream>
#include <stack>
using namespace std;

int a[100001], n;
stack<int> s;

bool f()
{
	for(int i = 1, j = 1; j <= n;)
	{
		if(s.empty() || s.top() != a[j])
		{
			if(i > n) return false;
			s.push(i);
			//cout << "push " << i << endl;
			++i;
		}
		else
		{
			//cout << "pop  " << s.top() << endl;
			s.pop();
			++j;
		}
	}
	
	return true;
}

int main(int argc, char const *argv[])
{
	int T;
	cin >> T;
	while(T--)
	{
		cin >> n;
		for(int i = 1; i <= n; ++i)
		{
			cin >> a[i];
		}
		cout << (f() ? "yes" : "no") << endl;
	}
	return 0;
}

c.cpp

#include <iostream>
#include <algorithm>
using namespace std;

int a[21][21] = {}, p[21], n;

int g(int i)
{
	int& x = p[i];
	int& y = p[i + 1];
	int& z = p[i + 2];
	return a[x][y] + a[y][z] + a[z][x];
}

int f()
{
	for(int i = 0; i < n; ++i)
	{
		p[i] = i;
	}

	int res = 300;

	do
	{
		int sum = 0;
		for(int i = 0; i < n; i += 3)
		{
			sum += g(i);
		}
		res = min(res, sum);
	} while(next_permutation(p, p + n));

	return res;
}

int main(int argc, char const *argv[])
{
	int T;
	cin >> T;
	while(T--)
	{
		cin >> n;
		for(int i = 0; i < n; ++i)
		{
			for(int j = 0; j < n; ++j)
			{
				cin >> a[i][j];
			}
		}
		cout << f() << endl;
	}
	return 0;
}

c1.cpp

#include <iostream>
#include <algorithm>
using namespace std;

const int INF = 8400;

int a[21][21] = {}, p[21], n;

int g(int i)
{
	int& x = p[i];
	int& y = p[i + 1];
	int& z = p[i + 2];
	return a[x][y] + a[y][z] + a[z][x];
}

void swap(int x, int y)
{
	int tmp = p[x];
	p[x] = p[y];
	p[y] = tmp;
}

int f(int l, int r)
{
	if(l + 3 > r) return g(l);

	int res = INF;

	for(int i = l + 1; i < r; ++i)
	{
		swap(l + 1, i);
		for(int j = i + 1; j < r; ++j)
		{
			swap(l + 2, j);
			int tmp = g(l) + f(l + 3, r);
			//cout << '\t' << g(l) + tmp << endl;
			if(tmp < res) res = tmp;
			swap(l + 2, j);	
		}
		swap(l + 1, i);
	}

	return res;
}

int main(int argc, char const *argv[])
{
	int T;
	cin >> T;
	while(T--)
	{
		cin >> n;
		for(int i = 0; i < n; ++i)
		{
			for(int j = 0; j < n; ++j)
			{
				cin >> a[i][j];
			}
		}

		for(int i = 0; i < n; ++i)
		{
			p[i] = i;
		}

		cout << f(0, n) << endl;
	}
	return 0;
}