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feat: add solutions to lc problem: No.2080 (#4074)
No.2080.Range Frequency Queries
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6 files changed

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‎solution/2000-2099/2080.Range Frequency Queries/README.md

+108-15
Original file line numberDiff line numberDiff line change
@@ -68,7 +68,7 @@ rangeFreqQuery.query(0, 11, 33); // 返回 2 。33 在整个子数组中出现 2
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<!-- solution:start -->
7070

71-
### 方法一：哈希表
71+
### 方法一：哈希表 + 二分查找
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我们用一个哈希表 $g$ 来存储每个值对应的下标数组。在构造函数中，我们遍历数组 $\textit{arr}$，将每个值对应的下标加入到哈希表中。
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@@ -215,20 +215,8 @@ class RangeFreqQuery {
215215
if (!idx) {
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return 0;
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}
218-
const search = (x: number): number => {
219-
let [l, r] = [0, idx.length];
220-
while (l < r) {
221-
const mid = (l + r) >> 1;
222-
if (idx[mid] >= x) {
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r = mid;
224-
} else {
225-
l = mid + 1;
226-
}
227-
}
228-
return l;
229-
};
230-
const l = search(left);
231-
const r = search(right + 1);
218+
const l = _.sortedIndex(idx, left);
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const r = _.sortedIndex(idx, right + 1);
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return r - l;
233221
}
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}
@@ -240,6 +228,111 @@ class RangeFreqQuery {
240228
*/
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```
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#### Rust
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```rust
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use std::collections::HashMap;
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struct RangeFreqQuery {
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g: HashMap<i32, Vec<usize>>,
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}
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impl RangeFreqQuery {
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fn new(arr: Vec<i32>) -> Self {
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let mut g = HashMap::new();
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for (i, &value) in arr.iter().enumerate() {
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g.entry(value).or_insert_with(Vec::new).push(i);
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}
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RangeFreqQuery { g }
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}
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fn query(&self, left: i32, right: i32, value: i32) -> i32 {
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if let Some(idx) = self.g.get(&value) {
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let l = idx.partition_point(|&x| x < left as usize);
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let r = idx.partition_point(|&x| x <= right as usize);
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return (r - l) as i32;
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}
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0
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}
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}
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```
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#### JavaScript
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```js
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/**
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* @param {number[]} arr
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*/
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var RangeFreqQuery = function (arr) {
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this.g = new Map();
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for (let i = 0; i < arr.length; ++i) {
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if (!this.g.has(arr[i])) {
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this.g.set(arr[i], []);
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}
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this.g.get(arr[i]).push(i);
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}
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};
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/**
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* @param {number} left
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* @param {number} right
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* @param {number} value
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* @return {number}
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*/
283+
RangeFreqQuery.prototype.query = function (left, right, value) {
284+
const idx = this.g.get(value);
285+
if (!idx) {
286+
return 0;
287+
}
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const l = _.sortedIndex(idx, left);
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const r = _.sortedIndex(idx, right + 1);
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return r - l;
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};
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/**
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* Your RangeFreqQuery object will be instantiated and called as such:
295+
* var obj = new RangeFreqQuery(arr)
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* var param_1 = obj.query(left,right,value)
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*/
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```
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300+
#### C#
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```cs
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public class RangeFreqQuery {
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private Dictionary<int, List<int>> g;
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public RangeFreqQuery(int[] arr) {
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g = new Dictionary<int, List<int>>();
308+
for (int i = 0; i < arr.Length; ++i) {
309+
if (!g.ContainsKey(arr[i])) {
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g[arr[i]] = new List<int>();
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}
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g[arr[i]].Add(i);
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}
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}
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public int Query(int left, int right, int value) {
317+
if (g.ContainsKey(value)) {
318+
var idx = g[value];
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int l = idx.BinarySearch(left);
320+
int r = idx.BinarySearch(right + 1);
321+
l = l < 0 ? -l - 1 : l;
322+
r = r < 0 ? -r - 1 : r;
323+
return r - l;
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}
325+
return 0;
326+
}
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}
328+
329+
/**
330+
* Your RangeFreqQuery object will be instantiated and called as such:
331+
* RangeFreqQuery obj = new RangeFreqQuery(arr);
332+
* int param_1 = obj.Query(left, right, value);
333+
*/
334+
```
335+
243336
<!-- tabs:end -->
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<!-- solution:end -->

‎solution/2000-2099/2080.Range Frequency Queries/README_EN.md

+108-15
Original file line numberDiff line numberDiff line change
@@ -67,7 +67,7 @@ rangeFreqQuery.query(0, 11, 33); // return 2. The value 33 occurs 2 times in the
6767

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<!-- solution:start -->
6969

70-
### Solution 1: Hash Table
70+
### Solution 1: Hash Table + Binary Search
7171

7272
We use a hash table $g$ to store the array of indices corresponding to each value. In the constructor, we traverse the array $\textit{arr}$, adding the index corresponding to each value to the hash table.
7373

@@ -214,20 +214,8 @@ class RangeFreqQuery {
214214
if (!idx) {
215215
return 0;
216216
}
217-
const search = (x: number): number => {
218-
let [l, r] = [0, idx.length];
219-
while (l < r) {
220-
const mid = (l + r) >> 1;
221-
if (idx[mid] >= x) {
222-
r = mid;
223-
} else {
224-
l = mid + 1;
225-
}
226-
}
227-
return l;
228-
};
229-
const l = search(left);
230-
const r = search(right + 1);
217+
const l = _.sortedIndex(idx, left);
218+
const r = _.sortedIndex(idx, right + 1);
231219
return r - l;
232220
}
233221
}
@@ -239,6 +227,111 @@ class RangeFreqQuery {
239227
*/
240228
```
241229

230+
#### Rust
231+
232+
```rust
233+
use std::collections::HashMap;
234+
235+
struct RangeFreqQuery {
236+
g: HashMap<i32, Vec<usize>>,
237+
}
238+
239+
impl RangeFreqQuery {
240+
fn new(arr: Vec<i32>) -> Self {
241+
let mut g = HashMap::new();
242+
for (i, &value) in arr.iter().enumerate() {
243+
g.entry(value).or_insert_with(Vec::new).push(i);
244+
}
245+
RangeFreqQuery { g }
246+
}
247+
248+
fn query(&self, left: i32, right: i32, value: i32) -> i32 {
249+
if let Some(idx) = self.g.get(&value) {
250+
let l = idx.partition_point(|&x| x < left as usize);
251+
let r = idx.partition_point(|&x| x <= right as usize);
252+
return (r - l) as i32;
253+
}
254+
0
255+
}
256+
}
257+
```
258+
259+
#### JavaScript
260+
261+
```js
262+
/**
263+
* @param {number[]} arr
264+
*/
265+
var RangeFreqQuery = function (arr) {
266+
this.g = new Map();
267+
268+
for (let i = 0; i < arr.length; ++i) {
269+
if (!this.g.has(arr[i])) {
270+
this.g.set(arr[i], []);
271+
}
272+
this.g.get(arr[i]).push(i);
273+
}
274+
};
275+
276+
/**
277+
* @param {number} left
278+
* @param {number} right
279+
* @param {number} value
280+
* @return {number}
281+
*/
282+
RangeFreqQuery.prototype.query = function (left, right, value) {
283+
const idx = this.g.get(value);
284+
if (!idx) {
285+
return 0;
286+
}
287+
const l = _.sortedIndex(idx, left);
288+
const r = _.sortedIndex(idx, right + 1);
289+
return r - l;
290+
};
291+
292+
/**
293+
* Your RangeFreqQuery object will be instantiated and called as such:
294+
* var obj = new RangeFreqQuery(arr)
295+
* var param_1 = obj.query(left,right,value)
296+
*/
297+
```
298+
299+
#### C#
300+
301+
```cs
302+
public class RangeFreqQuery {
303+
private Dictionary<int, List<int>> g;
304+
305+
public RangeFreqQuery(int[] arr) {
306+
g = new Dictionary<int, List<int>>();
307+
for (int i = 0; i < arr.Length; ++i) {
308+
if (!g.ContainsKey(arr[i])) {
309+
g[arr[i]] = new List<int>();
310+
}
311+
g[arr[i]].Add(i);
312+
}
313+
}
314+
315+
public int Query(int left, int right, int value) {
316+
if (g.ContainsKey(value)) {
317+
var idx = g[value];
318+
int l = idx.BinarySearch(left);
319+
int r = idx.BinarySearch(right + 1);
320+
l = l < 0 ? -l - 1 : l;
321+
r = r < 0 ? -r - 1 : r;
322+
return r - l;
323+
}
324+
return 0;
325+
}
326+
}
327+
328+
/**
329+
* Your RangeFreqQuery object will be instantiated and called as such:
330+
* RangeFreqQuery obj = new RangeFreqQuery(arr);
331+
* int param_1 = obj.Query(left, right, value);
332+
*/
333+
```
334+
242335
<!-- tabs:end -->
243336

244337
<!-- solution:end -->

‎solution/2000-2099/2080.Range Frequency Queries/Solution.cs

+31
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,31 @@
1+
public class RangeFreqQuery {
2+
private Dictionary<int, List<int>> g;
3+
4+
public RangeFreqQuery(int[] arr) {
5+
g = new Dictionary<int, List<int>>();
6+
for (int i = 0; i < arr.Length; ++i) {
7+
if (!g.ContainsKey(arr[i])) {
8+
g[arr[i]] = new List<int>();
9+
}
10+
g[arr[i]].Add(i);
11+
}
12+
}
13+
14+
public int Query(int left, int right, int value) {
15+
if (g.ContainsKey(value)) {
16+
var idx = g[value];
17+
int l = idx.BinarySearch(left);
18+
int r = idx.BinarySearch(right + 1);
19+
l = l < 0 ? -l - 1 : l;
20+
r = r < 0 ? -r - 1 : r;
21+
return r - l;
22+
}
23+
return 0;
24+
}
25+
}
26+
27+
/**
28+
* Your RangeFreqQuery object will be instantiated and called as such:
29+
* RangeFreqQuery obj = new RangeFreqQuery(arr);
30+
* int param_1 = obj.Query(left, right, value);
31+
*/

‎solution/2000-2099/2080.Range Frequency Queries/Solution.js

+35
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,35 @@
1+
/**
2+
* @param {number[]} arr
3+
*/
4+
var RangeFreqQuery = function (arr) {
5+
this.g = new Map();
6+
7+
for (let i = 0; i < arr.length; ++i) {
8+
if (!this.g.has(arr[i])) {
9+
this.g.set(arr[i], []);
10+
}
11+
this.g.get(arr[i]).push(i);
12+
}
13+
};
14+
15+
/**
16+
* @param {number} left
17+
* @param {number} right
18+
* @param {number} value
19+
* @return {number}
20+
*/
21+
RangeFreqQuery.prototype.query = function (left, right, value) {
22+
const idx = this.g.get(value);
23+
if (!idx) {
24+
return 0;
25+
}
26+
const l = _.sortedIndex(idx, left);
27+
const r = _.sortedIndex(idx, right + 1);
28+
return r - l;
29+
};
30+
31+
/**
32+
* Your RangeFreqQuery object will be instantiated and called as such:
33+
* var obj = new RangeFreqQuery(arr)
34+
* var param_1 = obj.query(left,right,value)
35+
*/

‎solution/2000-2099/2080.Range Frequency Queries/Solution.rs

+24
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,24 @@
1+
use std::collections::HashMap;
2+
3+
struct RangeFreqQuery {
4+
g: HashMap<i32, Vec<usize>>,
5+
}
6+
7+
impl RangeFreqQuery {
8+
fn new(arr: Vec<i32>) -> Self {
9+
let mut g = HashMap::new();
10+
for (i, &value) in arr.iter().enumerate() {
11+
g.entry(value).or_insert_with(Vec::new).push(i);
12+
}
13+
RangeFreqQuery { g }
14+
}
15+
16+
fn query(&self, left: i32, right: i32, value: i32) -> i32 {
17+
if let Some(idx) = self.g.get(&value) {
18+
let l = idx.partition_point(|&x| x < left as usize);
19+
let r = idx.partition_point(|&x| x <= right as usize);
20+
return (r - l) as i32;
21+
}
22+
0
23+
}
24+
}

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