OKX HK Hackerrank

没想到那么简单，求大米


T1: Given an array `arr` of `n` non-negative integers and an array `power` of `k` integers where `k` is an even number, perform the following operation in steps.

- Select two integers `i` and `j` such that `0 ≤ i < j < |power|`. In each operation, `i` and `j` are selected independently.
  - If `power[i] = power[j]`, add the summation of the subarray `arr[power[i]...power[j]]` to the power.
  - If `power[i] > power[j]`, add the summation of the subarray `arr[power[j]...power[i]]` to the power.
  - Delete `i`-th and `j`-th elements from `power`, and its length is reduced by 2.

Starting at 0 initial power, maximize the final power after exactly `k/2` operations. Return that maximum power modulo `(10^9 + 7)`.

**Note:** Subarray `arr[l...r]` denotes the subarray formed by the elements `arr[l], arr[l+1], ..., arr[r-1], arr[r]`.

#### Example:
```
arr = [3, 5, 6, 0, 7], power = [3, 1, 0, 2]
k = 4, the size of power, so perform k/2 = 2 operations.
```

One of the optimal approaches is shown:

```
- Select i=0, j=2. Here, power[0] = 3 and power[2] = 0. Add the sum of subarray `arr[0...3]` (3 + 5 + 6 + 0 = 14) to the power. 0 + 14 = 14. Remove the two elements from power, and power is [1, 2].
- Select i=0, j=1. Here, power[0] = 1 and power[1] = 2. Add the sum of subarray `arr[1...2]` 5 + 6 = 11, so power is 14 + 11 = 25.
```

题解

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T2:
Given a permutation `p` of length `n` denoted by `p = [p1, p2,..., pn]`, a number `k` is balanced if there are two indices `l`, `r` (1 ≤ l ≤ r ≤ n), such that the numbers `[p[l], p[l+1], ..., p[r]]` form a permutation of the numbers `1, 2, ..., k`.

For each `k` (1 ≤ k ≤ n), determine if it is a balanced number or not. Return a binary string `ans` of length `n`, where the `i-th` character of the string (considering 1-based indexing) is '1' if `i` is a balanced number and '0' otherwise.

**Note:** A permutation of length `n` contains each integer from 1 to `n` exactly once in any order.

#### Example:
Consider `n = 4`, `p = [4, 1, 3, 2]`.

- For `k = 1`: Choose `l = 2` and `r = 2`, the chosen `p[2:2] = {1}`, a permutation of length 1.
- For `k = 2`: No pair of indices results in a permutation of length 2. It is not a balanced number.
- For `k = 3`: `l = 2, r = 4, p[2:4] = [1, 3, 2], a permutation of length 3.
- For `k = 4`, `l = 1, r = 4, p[1:4] = [4, 1, 3, 2], a permutation of length 4.

The balanced numbers are 1, 3, and 4, while 2 is not balanced. The answer is `"1011"`.

题解

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选择题还是比较简单的

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同收到oa 请问你开始面试了吗

6godfather9 发表于 2024-12-6 06:25
同收到oa 请问你开始面试了吗

收到面试邀请了，还没开始面