Codeforces Round 543 (Div. 1, based on Technocup 2019 Final Round)
F
Secret Letters
Codeforces
3100
原题
← E→
翻译中…

Little W and Little P decided to send letters to each other regarding the most important events during a day. There are $n$ events during a day: at time moment $t_i$ something happens to the person $p_i$ ($p_i$ is either W or P, denoting Little W and Little P, respectively), so he needs to immediately send a letter to the other person. They can send a letter using one of the two ways:

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  • Ask Friendly O to deliver the letter directly. Friendly O takes $d$ acorns for each letter.
  • Leave the letter at Wise R's den. Wise R values free space, so he takes $c \cdot T$ acorns for storing a letter for a time segment of length $T$. The recipient can take a letter from Wise R either when he leaves his own letter at Wise R's den, or at time moment $t_{n + 1}$, when everybody comes to Wise R for a tea. It is not possible to take a letter from Wise R's den at other time moments. The friends can store as many letters at Wise R's den as they want, paying for each one separately.
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Help the friends determine the minimum possible total cost of sending all letters.

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Input

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The first line contains three integers $n, c, d$ ($1 \leq n \leq 10^5$, $1 \leq c \leq 10^2$, $1 \leq d \leq 10^8$) — the number of letters, the cost of storing a letter for one time unit at Wise R's den and the cost of delivering a letter via Friendly O.

翻译中…

The next $n$ describe the events. The $i$-th of them contains an integer $t_i$ and a character $p_i$ ($0 \leq t_i \leq 10^6$, $p_i$ is either W or P) — the time the $i$-th event happens and the person the event happens to.

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The last line contains a single integer $t_{n + 1}$ ($0 \leq t_{n+1} \leq 10^6$) — the time when everybody comes to Wise R for a tea and takes all remaining letters.

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It is guaranteed that $t_i \lt t_{i + 1}$ for all $i$ from $1$ to $n$.

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Output

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Print a single integer — the minimum possible cost of delivery of all letters.

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Note

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One of optimal solutions in the first example:

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  • At time moment 0 Little P leaves the letter at Wise R's den.
  • At time moment 1 Little W leaves his letter at Wise R's den and takes Little P's letter. This letter is at the den from time moment 0 to time moment 1, it costs $1$ acorn.
  • At time moment 3 Little P sends his letter via Friendly O, it costs $4$ acorns.
  • At time moment 5 Little P leaves his letter at the den, receiving Little W's letter which storage costs 4 acorns.
  • At time moment 8 Little P leaves one more letter at the den.
  • At time moment 10 Little W comes to the den for a tea and receives the two letters, paying 5 and 2 acorns.
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The total cost of delivery is thus $1 + 4 + 4 + 5 + 2 = 16$ acorns.

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样例

Input #1
5 1 4
0 P
1 W
3 P
5 P
8 P
10
Output #1
16
InputCopy OutputCopy
Input #2
10 10 94
17 W
20 W
28 W
48 W
51 P
52 W
56 W
62 P
75 P
78 P
87
Output #2
916
InputCopy OutputCopy
题目信息
题号
1120F
时间限制
2 s
内存限制
512 MB
标签
数据结构
动态规划
贪心

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。