# 比赛链接

https://codeforces.com/contest/1555

# 1. A. PizzaForces

## 1.1. 题意

6元15个物品，8元20个物品，10元25个物品

## 1.2. 做法

notes: 注意一定是至少两倍以上才能贪心

# 比赛链接

https://codeforces.com/contest/1551

# 比赛链接

VK Cup 2021 - Elimination (Engine)

# 题目大意：

$inv$ 为逆序对个数

# 做法：

$f(i,j) = \sum_{t \in [1,i]} f(i-1,j-t+1)$

\begin{aligned} ans[i] \&= i * ans[i-1] + \sum_{1<=u<v<=i, x+u>y+v} f(i-1,x)\cdot f(i-1,y) \&= i * ans[i-1] + \sum_{x-y>v-u, 1<=u<v<=i} f(i-1,x)\cdot f(i-1,y) \&= i * ans[i-1] + \sum_{x-y>d, 1<=d<i} (i-d)*f(i-1,x)\cdot f(i-1,y) \&= i * ans[i-1] + \sum_{x,y} f(i-1,x)\cdot f(i-1,y) \cdot \sum_{x-y>d, 1<=d<i} (i-d) \end{aligned}

## 第44届ICPC亚洲赛区南京站

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## 第44届ICPC亚洲赛区银川站

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## 2020牛客暑期多校训练营第七场

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# 比赛链接

http://codeforces.com/gym/102832

# A. Krypton

## 题意

$$\begin{array}{|c|c|c|} \hline \text{Price (RMB yuan)} & \text{Normal amount (coupons)} & \text{First recharge reward (coupons)} \ \hline 1 & 10 & 8 \ \hline 6 & 60 & 18 \ \hline 28 & 280 & 28 \ \hline 88 & 880 & 58 \ \hline 198 & 1980 & 128 \ \hline 328 & 3280 & 198 \ \hline 648 & 6480 & 388 \ \hline \end{array}$$

## 2020省赛网赛

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# 比赛链接

http://codeforces.com/gym/102798