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feat: add solutions to lc problem: No.2670 (doocs#2289)
No.2670.Find the Distinct Difference Array
1 parent f2a06e1 commit 9d2d6bb

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‎solution/2600-2699/2670.Find the Distinct Difference Array/README.md‎

Lines changed: 25 additions & 68 deletions
Original file line numberDiff line numberDiff line change
@@ -53,19 +53,30 @@
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## 解法
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56-
### 方法一
56+
### 方法一:哈希表 + 预处理后缀
57+
58+
我们可以预处理出一个后缀数组 $suf,ドル其中 $suf[i]$ 表示后缀 $nums[i, ..., n - 1]$ 中不同元素的数目,在预处理过程中,我们使用一个哈希表 $s$ 来维护后缀中出现过的元素,这样我们就可以在 $O(1)$ 的时间内查询后缀中不同元素的数目。
59+
60+
预处理完后缀数组 $suf$ 后,我们清空哈希表 $s,ドル然后再次遍历数组 $nums,ドル用哈希表 $s$ 来维护前缀中出现过的元素,那么位置 $i$ 的答案就是 $s$ 中不同元素的数目减去 $suf[i + 1],ドル即 $|s| - suf[i + 1]$。
61+
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时间复杂度 $O(n),ドル空间复杂度 $O(n)$。其中 $n$ 是数组 $nums$ 的长度。
5763

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<!-- tabs:start -->
5965

6066
```python
6167
class Solution:
6268
def distinctDifferenceArray(self, nums: List[int]) -> List[int]:
6369
n = len(nums)
70+
suf = [0] * (n + 1)
71+
s = set()
72+
for i in range(n - 1, -1, -1):
73+
s.add(nums[i])
74+
suf[i] = len(s)
75+
s.clear()
6476
ans = [0] * n
65-
for i in range(n):
66-
a = len(set(nums[: i + 1]))
67-
b = len(set(nums[i + 1 :]))
68-
ans[i] = a - b
77+
for i, x in enumerate(nums):
78+
s.add(x)
79+
ans[i] = len(s) - suf[i + 1]
6980
return ans
7081
```
7182

@@ -134,14 +145,14 @@ func distinctDifferenceArray(nums []int) []int {
134145
```ts
135146
function distinctDifferenceArray(nums: number[]): number[] {
136147
const n = nums.length;
137-
const suf: number[] = newArray(n + 1).fill(0);
148+
const suf: number[] = Array(n + 1).fill(0);
138149
const s: Set<number> = new Set();
139150
for (let i = n - 1; i >= 0; --i) {
140151
s.add(nums[i]);
141152
suf[i] = s.size;
142153
}
143154
s.clear();
144-
const ans: number[] = newArray(n);
155+
const ans: number[] = Array(n).fill(0);
145156
for (let i = 0; i < n; ++i) {
146157
s.add(nums[i]);
147158
ans[i] = s.size - suf[i + 1];
@@ -153,76 +164,22 @@ function distinctDifferenceArray(nums: number[]): number[] {
153164
```rust
154165
use std::collections::HashSet;
155166

156-
impl Solution {
157-
pub fn distinct_difference_array(nums: Vec<i32>) -> Vec<i32> {
158-
let mut ans: Vec<i32> = Vec::new();
159-
160-
for i in 0..nums.len() {
161-
let mut j = 0;
162-
let mut hash1 = HashSet::new();
163-
while j <= i {
164-
hash1.insert(nums[j]);
165-
j += 1;
166-
}
167-
168-
let mut k = i + 1;
169-
let mut hash2 = HashSet::new();
170-
while k < nums.len() {
171-
hash2.insert(nums[k]);
172-
k += 1;
173-
}
174-
175-
ans.push((hash1.len() - hash2.len()) as i32);
176-
}
177-
178-
ans
179-
}
180-
}
181-
```
182-
183-
<!-- tabs:end -->
184-
185-
### 方法二
186-
187-
<!-- tabs:start -->
188-
189-
```python
190-
class Solution:
191-
def distinctDifferenceArray(self, nums: List[int]) -> List[int]:
192-
n = len(nums)
193-
suf = [0] * (n + 1)
194-
s = set()
195-
for i in range(n - 1, -1, -1):
196-
s.add(nums[i])
197-
suf[i] = len(s)
198-
199-
s.clear()
200-
ans = [0] * n
201-
for i, x in enumerate(nums):
202-
s.add(x)
203-
ans[i] = len(s) - suf[i + 1]
204-
return ans
205-
```
206-
207-
```rust
208-
use std::collections::HashSet;
209-
210167
impl Solution {
211168
pub fn distinct_difference_array(nums: Vec<i32>) -> Vec<i32> {
212169
let n = nums.len();
213-
let mut s = vec![0; n + 1];
214-
let mut set = HashSet::new();
170+
let mut suf = vec![0; n + 1];
171+
let mut s = HashSet::new();
215172

216173
for i in (0..n).rev() {
217-
set.insert(nums[i]);
218-
s[i] = set.len();
174+
s.insert(nums[i]);
175+
suf[i] = s.len();
219176
}
220177

221178
let mut ans = Vec::new();
222-
set.clear();
179+
s.clear();
223180
for i in 0..n {
224-
set.insert(nums[i]);
225-
ans.push((set.len() - s[i + 1]) as i32);
181+
s.insert(nums[i]);
182+
ans.push((s.len() - suf[i + 1]) as i32);
226183
}
227184

228185
ans

‎solution/2600-2699/2670.Find the Distinct Difference Array/README_EN.md‎

Lines changed: 25 additions & 68 deletions
Original file line numberDiff line numberDiff line change
@@ -47,19 +47,30 @@ For index i = 4, there are 3 distinct elements in the prefix and no elements in
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4848
## Solutions
4949

50-
### Solution 1
50+
### Solution 1: Hash Table + Preprocessed Suffix
51+
52+
We can preprocess a suffix array $suf,ドル where $suf[i]$ represents the number of distinct elements in the suffix $nums[i, ..., n - 1]$. During the preprocessing, we use a hash table $s$ to maintain the elements that have appeared in the suffix, so we can query the number of distinct elements in the suffix in $O(1)$ time.
53+
54+
After preprocessing the suffix array $suf,ドル we clear the hash table $s,ドル and then traverse the array $nums$ again, using the hash table $s$ to maintain the elements that have appeared in the prefix. The answer at position $i$ is the number of distinct elements in $s$ minus $suf[i + 1],ドル that is, $s.size() - suf[i + 1]$.
55+
56+
The time complexity is $O(n),ドル and the space complexity is $O(n)$. Here, $n$ is the length of the array $nums$.
5157

5258
<!-- tabs:start -->
5359

5460
```python
5561
class Solution:
5662
def distinctDifferenceArray(self, nums: List[int]) -> List[int]:
5763
n = len(nums)
64+
suf = [0] * (n + 1)
65+
s = set()
66+
for i in range(n - 1, -1, -1):
67+
s.add(nums[i])
68+
suf[i] = len(s)
69+
s.clear()
5870
ans = [0] * n
59-
for i in range(n):
60-
a = len(set(nums[: i + 1]))
61-
b = len(set(nums[i + 1 :]))
62-
ans[i] = a - b
71+
for i, x in enumerate(nums):
72+
s.add(x)
73+
ans[i] = len(s) - suf[i + 1]
6374
return ans
6475
```
6576

@@ -128,14 +139,14 @@ func distinctDifferenceArray(nums []int) []int {
128139
```ts
129140
function distinctDifferenceArray(nums: number[]): number[] {
130141
const n = nums.length;
131-
const suf: number[] = newArray(n + 1).fill(0);
142+
const suf: number[] = Array(n + 1).fill(0);
132143
const s: Set<number> = new Set();
133144
for (let i = n - 1; i >= 0; --i) {
134145
s.add(nums[i]);
135146
suf[i] = s.size;
136147
}
137148
s.clear();
138-
const ans: number[] = newArray(n);
149+
const ans: number[] = Array(n).fill(0);
139150
for (let i = 0; i < n; ++i) {
140151
s.add(nums[i]);
141152
ans[i] = s.size - suf[i + 1];
@@ -147,76 +158,22 @@ function distinctDifferenceArray(nums: number[]): number[] {
147158
```rust
148159
use std::collections::HashSet;
149160

150-
impl Solution {
151-
pub fn distinct_difference_array(nums: Vec<i32>) -> Vec<i32> {
152-
let mut ans: Vec<i32> = Vec::new();
153-
154-
for i in 0..nums.len() {
155-
let mut j = 0;
156-
let mut hash1 = HashSet::new();
157-
while j <= i {
158-
hash1.insert(nums[j]);
159-
j += 1;
160-
}
161-
162-
let mut k = i + 1;
163-
let mut hash2 = HashSet::new();
164-
while k < nums.len() {
165-
hash2.insert(nums[k]);
166-
k += 1;
167-
}
168-
169-
ans.push((hash1.len() - hash2.len()) as i32);
170-
}
171-
172-
ans
173-
}
174-
}
175-
```
176-
177-
<!-- tabs:end -->
178-
179-
### Solution 2
180-
181-
<!-- tabs:start -->
182-
183-
```python
184-
class Solution:
185-
def distinctDifferenceArray(self, nums: List[int]) -> List[int]:
186-
n = len(nums)
187-
suf = [0] * (n + 1)
188-
s = set()
189-
for i in range(n - 1, -1, -1):
190-
s.add(nums[i])
191-
suf[i] = len(s)
192-
193-
s.clear()
194-
ans = [0] * n
195-
for i, x in enumerate(nums):
196-
s.add(x)
197-
ans[i] = len(s) - suf[i + 1]
198-
return ans
199-
```
200-
201-
```rust
202-
use std::collections::HashSet;
203-
204161
impl Solution {
205162
pub fn distinct_difference_array(nums: Vec<i32>) -> Vec<i32> {
206163
let n = nums.len();
207-
let mut s = vec![0; n + 1];
208-
let mut set = HashSet::new();
164+
let mut suf = vec![0; n + 1];
165+
let mut s = HashSet::new();
209166

210167
for i in (0..n).rev() {
211-
set.insert(nums[i]);
212-
s[i] = set.len();
168+
s.insert(nums[i]);
169+
suf[i] = s.len();
213170
}
214171

215172
let mut ans = Vec::new();
216-
set.clear();
173+
s.clear();
217174
for i in 0..n {
218-
set.insert(nums[i]);
219-
ans.push((set.len() - s[i + 1]) as i32);
175+
s.insert(nums[i]);
176+
ans.push((s.len() - suf[i + 1]) as i32);
220177
}
221178

222179
ans
Lines changed: 9 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1,9 +1,14 @@
11
class Solution:
22
def distinctDifferenceArray(self, nums: List[int]) -> List[int]:
33
n = len(nums)
4+
suf = [0] * (n + 1)
5+
s = set()
6+
for i in range(n - 1, -1, -1):
7+
s.add(nums[i])
8+
suf[i] = len(s)
9+
s.clear()
410
ans = [0] * n
5-
for i in range(n):
6-
a = len(set(nums[: i + 1]))
7-
b = len(set(nums[i + 1 :]))
8-
ans[i] = a - b
11+
for i, x in enumerate(nums):
12+
s.add(x)
13+
ans[i] = len(s) - suf[i + 1]
914
return ans

‎solution/2600-2699/2670.Find the Distinct Difference Array/Solution.rs‎

Lines changed: 12 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -2,24 +2,20 @@ use std::collections::HashSet;
22

33
impl Solution {
44
pub fn distinct_difference_array(nums: Vec<i32>) -> Vec<i32> {
5-
let mut ans: Vec<i32> = Vec::new();
5+
let n = nums.len();
6+
let mut suf = vec![0; n + 1];
7+
let mut s = HashSet::new();
68

7-
for i in 0..nums.len() {
8-
let mut j = 0;
9-
let mut hash1 = HashSet::new();
10-
while j <= i {
11-
hash1.insert(nums[j]);
12-
j += 1;
13-
}
14-
15-
let mut k = i + 1;
16-
let mut hash2 = HashSet::new();
17-
while k < nums.len() {
18-
hash2.insert(nums[k]);
19-
k += 1;
20-
}
9+
for i in (0..n).rev() {
10+
s.insert(nums[i]);
11+
suf[i] = s.len();
12+
}
2113

22-
ans.push((hash1.len() - hash2.len()) as i32);
14+
let mut ans = Vec::new();
15+
s.clear();
16+
for i in 0..n {
17+
s.insert(nums[i]);
18+
ans.push((s.len() - suf[i + 1]) as i32);
2319
}
2420

2521
ans

‎solution/2600-2699/2670.Find the Distinct Difference Array/Solution.ts‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,13 +1,13 @@
11
function distinctDifferenceArray(nums: number[]): number[] {
22
const n = nums.length;
3-
const suf: number[] = newArray(n + 1).fill(0);
3+
const suf: number[] = Array(n + 1).fill(0);
44
const s: Set<number> = new Set();
55
for (let i = n - 1; i >= 0; --i) {
66
s.add(nums[i]);
77
suf[i] = s.size;
88
}
99
s.clear();
10-
const ans: number[] = newArray(n);
10+
const ans: number[] = Array(n).fill(0);
1111
for (let i = 0; i < n; ++i) {
1212
s.add(nums[i]);
1313
ans[i] = s.size - suf[i + 1];

‎solution/2600-2699/2670.Find the Distinct Difference Array/Solution2.py‎

Lines changed: 0 additions & 15 deletions
This file was deleted.

‎solution/2600-2699/2670.Find the Distinct Difference Array/Solution2.rs‎

Lines changed: 0 additions & 23 deletions
This file was deleted.

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