Codeforces Round #551 (Div. 2) 小结

A.无法用言语形容...一直被大佬搞，刚才从新读了遍题，是自己沙雕了

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
//typedef __int128 bll;
const ll maxn = 1e5+100;
const ll mod = 1e9+7;
const ld pi = acos(-1.0);
const ll inf = 1e18;
const ld eps = 1e-5;
const ld e = exp(1);

ll n,t,ans,mi = inf;

int main()
{	
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
	
	cin >> n >> t;
	
	for(ll i = 1; i <= n; i++)
	{
		ll a,b;
		cin >> a >> b;
		
		if(t == a)
		{
			mi = -inf;
			ans = i;
		}
		else if(t > a)
		{
			while(a < t)
			{
				a+=b;
			}
			if(a-t < mi)
			{
				mi = a-t;
				ans = i;	
			}	
			
		}
		else if(t < a)
		{
			if(a - t < mi)
			{
				mi = a-t;
				ans = i;
			}
		}
	}
	
	cout << ans << endl;
	
	
	return 0;
}

 B.根据题意构造图形即可，因为输出任一合法的图形就OK，所以此题就很简单了

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
//typedef __int128 bll;
const ll maxn = 1e2+100;
const ll mod = 1e9+7;
const ld pi = acos(-1.0);
const ll inf = 1e18;
const ld eps = 1e-5;
const ld e = exp(1);

ll n,m,h,a[maxn],ans[maxn][maxn],b[maxn];

int main()
{	
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
	
	cin >> n >> m >> h;
	
	for(ll i = 1; i <= m; i++)
	{
		cin >> a[i];
	}
	
	for(ll i = 1; i <= n; i++)
	{
		cin >> b[i];
	}
	
	for(ll i = 1; i <= n; i++)
	{
		for(ll j = 1; j <= m; j++)
		{
			ll x;
			cin >> x;
			
			if(x == 1)
			{
				ans[i][j] = min(b[i],a[j]);
			}
			else
			{
				ans[i][j] = 0;
			}
			
		}
	}
	
	for(ll i = 1; i <= n; i++)
	{
		for(ll j = 1; j <= m; j++)
		{
			cout << ans[i][j] << " ";
		}
		cout << endl;
	}
	
	
	return 0;
}

 C。题意是要求你前缀非法，但是整个字符串要合法，也就是在左括号比右括号多的情况下构造即可（疯狂放左括号啊！）

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
//typedef __int128 bll;
const ll maxn = 3e5+100;
const ll mod = 1e9+7;
const ld pi = acos(-1.0);
const ll inf = 1e18;
const ld eps = 1e-5;
const ld e = exp(1);

ll len,l,r,sum;
char str[maxn];

int main()
{	
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
	
	cin >> len;
	cin >> str+1;
	
	
	if(len%2 == 1)
	{
		cout << ":(" << endl;
	}
	else
	{
		ll l = 0,r = 0;
		for(ll i = 1; i <= len; i++)
		{
			if(str[i] == '(')
				l++;
			else if(str[i] == ')')
				r++;
		}
		
		ll k1 = len/2 - l,k2 = len/2 - r;
		
		for(ll i = 1; i <= len; i++)
		{
			if(str[i] == '?')
			{
				if(k1)
				{
					k1--;
					str[i] = '(';
				}
				else if(k2)
				{
					k2--;
					str[i] = ')';
				}
			}
		}
		
//		for(ll i = 1; i <= len; i++)
//			cout << str[i];
//		cout << endl;
		
		bool flag = true;
		ll sum = 0;
		for(ll i = 1; i <= len-1 && flag == true; i++)
		{
			if(str[i] == '(')
			{
				sum -= 1;
			}
			else
				sum += 1;
				
			if(sum >=0 )
				flag = false;
		}
		
		if(flag && str[len] == ')')
		{
			for(ll i = 1; i <= len; i++)
				cout << str[i];
			cout << endl;
		}
		else
		{
			cout << ":(" << endl;
		}	
	}

	return 0;
}

D.树形DP...等候更新