2218.Maximum Value of K Coins From Piles
===
###### tags: `Hard`,`Array`,`DP`,`Prefix Sum`
[2218. Maximum Value of K Coins From Piles](https://leetcode.com/problems/maximum-value-of-k-coins-from-piles/)
### 題目描述
There are `n` **piles** of coins on a table. Each pile consists of a **positive number** of coins of assorted denominations.
In one move, you can choose any coin on **top** of any pile, remove it, and add it to your wallet.
Given a list `piles`, where `piles[i]` is a list of integers denoting the composition of the i^th^ pile from **top to bottom**, and a positive integer `k`, return* the **maximum total value** of coins you can have in your wallet if you choose **exactly*** `k` *coins optimally.*
### 範例
**Example 1:**
![](https://assets.leetcode.com/uploads/2019/11/09/e1.png =80%x)
```
Input: piles = [[1,100,3],[7,8,9]], k = 2
Output: 101
Explanation:
The above diagram shows the different ways we can choose k coins.
The maximum total we can obtain is 101.
```
**Example 2:**
```
Input: piles = [[100],[100],[100],[100],[100],[100],[1,1,1,1,1,1,700]], k = 7
Output: 706
Explanation:
The maximum total can be obtained if we choose all coins from the last pile.
```
**Constraints**:
* `n` == `piles.length`
* 1 <= `n` <= 1000
* 1 <= `piles[i][j]` <= 10^5^
* 1 <= `k` <= `sum(piles[i].length)` <= 2000
### 解答
### Reference
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