Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly
Sign up
Appearance settings

Commit 297d171

Browse files
feat: add solutions to lc problem: No.2671 (doocs#2290)
No.2671.Frequency Tracker
1 parent 9d2d6bb commit 297d171

File tree

7 files changed

+106
-146
lines changed

7 files changed

+106
-146
lines changed

‎solution/2600-2699/2671.Frequency Tracker/README.md‎

Lines changed: 39 additions & 49 deletions
Original file line numberDiff line numberDiff line change
@@ -79,7 +79,17 @@ frequencyTracker.hasFrequency(1); // 返回 true ,因为 3 出现 1 次
7979

8080
## 解法
8181

82-
### 方法一
82+
### 方法一:哈希表
83+
84+
我们定义两个哈希表,其中 $cnt$ 用于记录每个数字出现的次数,而 $freq$ 用于记录每个出现次数的数字的个数。
85+
86+
对于 `add` 操作,我们直接将哈希表 $freq$ 中 $cnt[number]$ 对应的值减一,然后将 $cnt[number]$ 加一,再将 $freq[cnt[number]]$ 对应的值加一。
87+
88+
对于 `deleteOne` 操作,我们首先判断 $cnt[number]$ 是否大于零,如果大于零,我们将哈希表 $freq$ 中 $cnt[number]$ 对应的值减一,然后将 $cnt[number]$ 减一,再将 $freq[cnt[number]]$ 对应的值加一。
89+
90+
对于 `hasFrequency` 操作,我们直接返回 $freq[frequency]$ 是否大于零。
91+
92+
时间复杂度方面,由于我们使用了哈希表,因此每个操作的时间复杂度均为 $O(1)$。空间复杂度 $O(n),ドル其中 $n$ 为不同的数字的个数。
8393

8494
<!-- tabs:start -->
8595

@@ -90,17 +100,15 @@ class FrequencyTracker:
90100
self.freq = defaultdict(int)
91101

92102
def add(self, number: int) -> None:
93-
if self.freq[self.cnt[number]] > 0:
94-
self.freq[self.cnt[number]] -= 1
103+
self.freq[self.cnt[number]] -= 1
95104
self.cnt[number] += 1
96105
self.freq[self.cnt[number]] += 1
97106

98107
def deleteOne(self, number: int) -> None:
99-
if self.cnt[number] == 0:
100-
return
101-
self.freq[self.cnt[number]] -= 1
102-
self.cnt[number] -= 1
103-
self.freq[self.cnt[number]] += 1
108+
if self.cnt[number]:
109+
self.freq[self.cnt[number]] -= 1
110+
self.cnt[number] -= 1
111+
self.freq[self.cnt[number]] += 1
104112

105113
def hasFrequency(self, frequency: int) -> bool:
106114
return self.freq[frequency] > 0
@@ -122,22 +130,17 @@ class FrequencyTracker {
122130
}
123131

124132
public void add(int number) {
125-
int f = cnt.getOrDefault(number, 0);
126-
if (freq.getOrDefault(f, 0) > 0) {
127-
freq.merge(f, -1, Integer::sum);
128-
}
133+
freq.merge(cnt.getOrDefault(number, 0), -1, Integer::sum);
129134
cnt.merge(number, 1, Integer::sum);
130-
freq.merge(f +1, 1, Integer::sum);
135+
freq.merge(cnt.get(number), 1, Integer::sum);
131136
}
132137

133138
public void deleteOne(int number) {
134-
int f = cnt.getOrDefault(number, 0);
135-
if (f == 0) {
136-
return;
139+
if (cnt.getOrDefault(number, 0) > 0) {
140+
freq.merge(cnt.get(number), -1, Integer::sum);
141+
cnt.merge(number, -1, Integer::sum);
142+
freq.merge(cnt.get(number), 1, Integer::sum);
137143
}
138-
freq.merge(f, -1, Integer::sum);
139-
cnt.merge(number, -1, Integer::sum);
140-
freq.merge(f - 1, 1, Integer::sum);
141144
}
142145

143146
public boolean hasFrequency(int frequency) {
@@ -161,22 +164,17 @@ public:
161164
}
162165

163166
void add(int number) {
164-
int f = cnt[number];
165-
if (f > 0) {
166-
freq[f]--;
167-
}
167+
freq[cnt[number]]--;
168168
cnt[number]++;
169-
freq[f + 1]++;
169+
freq[cnt[number]]++;
170170
}
171171

172172
void deleteOne(int number) {
173-
int f = cnt[number];
174-
if (f == 0) {
175-
return;
173+
if (cnt[number]) {
174+
freq[cnt[number]]--;
175+
cnt[number]--;
176+
freq[cnt[number]]++;
176177
}
177-
freq[f]--;
178-
cnt[number]--;
179-
freq[f - 1]++;
180178
}
181179

182180
bool hasFrequency(int frequency) {
@@ -208,22 +206,17 @@ func Constructor() FrequencyTracker {
208206
}
209207
210208
func (this *FrequencyTracker) Add(number int) {
211-
f := this.cnt[number]
212-
if f > 0 {
213-
this.freq[f]--
214-
}
209+
this.freq[this.cnt[number]]--
215210
this.cnt[number]++
216-
this.freq[f+1]++
211+
this.freq[this.cnt[number]]++
217212
}
218213
219214
func (this *FrequencyTracker) DeleteOne(number int) {
220-
f := this.cnt[number]
221-
if f == 0 {
222-
return
215+
if this.cnt[number] > 0 {
216+
this.freq[this.cnt[number]]--
217+
this.cnt[number]--
218+
this.freq[this.cnt[number]]++
223219
}
224-
this.freq[f]--
225-
this.cnt[number]--
226-
this.freq[f-1]++
227220
}
228221
229222
func (this *FrequencyTracker) HasFrequency(frequency int) bool {
@@ -251,21 +244,18 @@ class FrequencyTracker {
251244

252245
add(number: number): void {
253246
const f = this.cnt.get(number) || 0;
254-
if (f > 0) {
255-
this.freq.set(f, (this.freq.get(f) || 0) - 1);
256-
}
247+
this.freq.set(f, (this.freq.get(f) || 0) - 1);
257248
this.cnt.set(number, f + 1);
258249
this.freq.set(f + 1, (this.freq.get(f + 1) || 0) + 1);
259250
}
260251

261252
deleteOne(number: number): void {
262253
const f = this.cnt.get(number) || 0;
263-
if (f === 0) {
264-
return;
254+
if (f > 0) {
255+
this.freq.set(f, (this.freq.get(f) || 0) - 1);
256+
this.cnt.set(number, f - 1);
257+
this.freq.set(f - 1, (this.freq.get(f - 1) || 0) + 1);
265258
}
266-
this.freq.set(f, (this.freq.get(f) || 0) - 1);
267-
this.cnt.set(number, f - 1);
268-
this.freq.set(f - 1, (this.freq.get(f - 1) || 0) + 1);
269259
}
270260

271261
hasFrequency(frequency: number): boolean {

‎solution/2600-2699/2671.Frequency Tracker/README_EN.md‎

Lines changed: 39 additions & 49 deletions
Original file line numberDiff line numberDiff line change
@@ -78,7 +78,17 @@ frequencyTracker.hasFrequency(1); // Returns true, because 3 occurs once
7878

7979
## Solutions
8080

81-
### Solution 1
81+
### Solution 1: Hash Table
82+
83+
We define two hash tables, where $cnt$ is used to record the occurrence count of each number, and $freq$ is used to record the count of numbers with each frequency.
84+
85+
For the `add` operation, we directly decrement the value corresponding to $cnt[number]$ in the hash table $freq,ドル then increment $cnt[number],ドル and finally increment the value corresponding to $cnt[number]$ in $freq$.
86+
87+
For the `deleteOne` operation, we first check if $cnt[number]$ is greater than zero. If it is, we decrement the value corresponding to $cnt[number]$ in the hash table $freq,ドル then decrement $cnt[number],ドル and finally increment the value corresponding to $cnt[number]$ in $freq$.
88+
89+
For the `hasFrequency` operation, we directly return whether $freq[frequency]$ is greater than zero.
90+
91+
In terms of time complexity, since we use hash tables, the time complexity of each operation is $O(1)$. The space complexity is $O(n),ドル where $n$ is the number of distinct numbers.
8292

8393
<!-- tabs:start -->
8494

@@ -89,17 +99,15 @@ class FrequencyTracker:
8999
self.freq = defaultdict(int)
90100

91101
def add(self, number: int) -> None:
92-
if self.freq[self.cnt[number]] > 0:
93-
self.freq[self.cnt[number]] -= 1
102+
self.freq[self.cnt[number]] -= 1
94103
self.cnt[number] += 1
95104
self.freq[self.cnt[number]] += 1
96105

97106
def deleteOne(self, number: int) -> None:
98-
if self.cnt[number] == 0:
99-
return
100-
self.freq[self.cnt[number]] -= 1
101-
self.cnt[number] -= 1
102-
self.freq[self.cnt[number]] += 1
107+
if self.cnt[number]:
108+
self.freq[self.cnt[number]] -= 1
109+
self.cnt[number] -= 1
110+
self.freq[self.cnt[number]] += 1
103111

104112
def hasFrequency(self, frequency: int) -> bool:
105113
return self.freq[frequency] > 0
@@ -121,22 +129,17 @@ class FrequencyTracker {
121129
}
122130

123131
public void add(int number) {
124-
int f = cnt.getOrDefault(number, 0);
125-
if (freq.getOrDefault(f, 0) > 0) {
126-
freq.merge(f, -1, Integer::sum);
127-
}
132+
freq.merge(cnt.getOrDefault(number, 0), -1, Integer::sum);
128133
cnt.merge(number, 1, Integer::sum);
129-
freq.merge(f +1, 1, Integer::sum);
134+
freq.merge(cnt.get(number), 1, Integer::sum);
130135
}
131136

132137
public void deleteOne(int number) {
133-
int f = cnt.getOrDefault(number, 0);
134-
if (f == 0) {
135-
return;
138+
if (cnt.getOrDefault(number, 0) > 0) {
139+
freq.merge(cnt.get(number), -1, Integer::sum);
140+
cnt.merge(number, -1, Integer::sum);
141+
freq.merge(cnt.get(number), 1, Integer::sum);
136142
}
137-
freq.merge(f, -1, Integer::sum);
138-
cnt.merge(number, -1, Integer::sum);
139-
freq.merge(f - 1, 1, Integer::sum);
140143
}
141144

142145
public boolean hasFrequency(int frequency) {
@@ -160,22 +163,17 @@ public:
160163
}
161164

162165
void add(int number) {
163-
int f = cnt[number];
164-
if (f > 0) {
165-
freq[f]--;
166-
}
166+
freq[cnt[number]]--;
167167
cnt[number]++;
168-
freq[f + 1]++;
168+
freq[cnt[number]]++;
169169
}
170170

171171
void deleteOne(int number) {
172-
int f = cnt[number];
173-
if (f == 0) {
174-
return;
172+
if (cnt[number]) {
173+
freq[cnt[number]]--;
174+
cnt[number]--;
175+
freq[cnt[number]]++;
175176
}
176-
freq[f]--;
177-
cnt[number]--;
178-
freq[f - 1]++;
179177
}
180178

181179
bool hasFrequency(int frequency) {
@@ -207,22 +205,17 @@ func Constructor() FrequencyTracker {
207205
}
208206
209207
func (this *FrequencyTracker) Add(number int) {
210-
f := this.cnt[number]
211-
if f > 0 {
212-
this.freq[f]--
213-
}
208+
this.freq[this.cnt[number]]--
214209
this.cnt[number]++
215-
this.freq[f+1]++
210+
this.freq[this.cnt[number]]++
216211
}
217212
218213
func (this *FrequencyTracker) DeleteOne(number int) {
219-
f := this.cnt[number]
220-
if f == 0 {
221-
return
214+
if this.cnt[number] > 0 {
215+
this.freq[this.cnt[number]]--
216+
this.cnt[number]--
217+
this.freq[this.cnt[number]]++
222218
}
223-
this.freq[f]--
224-
this.cnt[number]--
225-
this.freq[f-1]++
226219
}
227220
228221
func (this *FrequencyTracker) HasFrequency(frequency int) bool {
@@ -250,21 +243,18 @@ class FrequencyTracker {
250243

251244
add(number: number): void {
252245
const f = this.cnt.get(number) || 0;
253-
if (f > 0) {
254-
this.freq.set(f, (this.freq.get(f) || 0) - 1);
255-
}
246+
this.freq.set(f, (this.freq.get(f) || 0) - 1);
256247
this.cnt.set(number, f + 1);
257248
this.freq.set(f + 1, (this.freq.get(f + 1) || 0) + 1);
258249
}
259250

260251
deleteOne(number: number): void {
261252
const f = this.cnt.get(number) || 0;
262-
if (f === 0) {
263-
return;
253+
if (f > 0) {
254+
this.freq.set(f, (this.freq.get(f) || 0) - 1);
255+
this.cnt.set(number, f - 1);
256+
this.freq.set(f - 1, (this.freq.get(f - 1) || 0) + 1);
264257
}
265-
this.freq.set(f, (this.freq.get(f) || 0) - 1);
266-
this.cnt.set(number, f - 1);
267-
this.freq.set(f - 1, (this.freq.get(f - 1) || 0) + 1);
268258
}
269259

270260
hasFrequency(frequency: number): boolean {

‎solution/2600-2699/2671.Frequency Tracker/Solution.cpp‎

Lines changed: 6 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -4,22 +4,17 @@ class FrequencyTracker {
44
}
55

66
void add(int number) {
7-
int f = cnt[number];
8-
if (f > 0) {
9-
freq[f]--;
10-
}
7+
freq[cnt[number]]--;
118
cnt[number]++;
12-
freq[f + 1]++;
9+
freq[cnt[number]]++;
1310
}
1411

1512
void deleteOne(int number) {
16-
int f = cnt[number];
17-
if (f == 0) {
18-
return;
13+
if (cnt[number]) {
14+
freq[cnt[number]]--;
15+
cnt[number]--;
16+
freq[cnt[number]]++;
1917
}
20-
freq[f]--;
21-
cnt[number]--;
22-
freq[f - 1]++;
2318
}
2419

2520
bool hasFrequency(int frequency) {

‎solution/2600-2699/2671.Frequency Tracker/Solution.go‎

Lines changed: 6 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -8,22 +8,17 @@ func Constructor() FrequencyTracker {
88
}
99

1010
func (this *FrequencyTracker) Add(number int) {
11-
f := this.cnt[number]
12-
if f > 0 {
13-
this.freq[f]--
14-
}
11+
this.freq[this.cnt[number]]--
1512
this.cnt[number]++
16-
this.freq[f+1]++
13+
this.freq[this.cnt[number]]++
1714
}
1815

1916
func (this *FrequencyTracker) DeleteOne(number int) {
20-
f := this.cnt[number]
21-
if f == 0 {
22-
return
17+
if this.cnt[number] > 0 {
18+
this.freq[this.cnt[number]]--
19+
this.cnt[number]--
20+
this.freq[this.cnt[number]]++
2321
}
24-
this.freq[f]--
25-
this.cnt[number]--
26-
this.freq[f-1]++
2722
}
2823

2924
func (this *FrequencyTracker) HasFrequency(frequency int) bool {

‎solution/2600-2699/2671.Frequency Tracker/Solution.java‎

Lines changed: 6 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -6,22 +6,17 @@ public FrequencyTracker() {
66
}
77

88
public void add(int number) {
9-
int f = cnt.getOrDefault(number, 0);
10-
if (freq.getOrDefault(f, 0) > 0) {
11-
freq.merge(f, -1, Integer::sum);
12-
}
9+
freq.merge(cnt.getOrDefault(number, 0), -1, Integer::sum);
1310
cnt.merge(number, 1, Integer::sum);
14-
freq.merge(f + 1, 1, Integer::sum);
11+
freq.merge(cnt.get(number), 1, Integer::sum);
1512
}
1613

1714
public void deleteOne(int number) {
18-
int f = cnt.getOrDefault(number, 0);
19-
if (f == 0) {
20-
return;
15+
if (cnt.getOrDefault(number, 0) > 0) {
16+
freq.merge(cnt.get(number), -1, Integer::sum);
17+
cnt.merge(number, -1, Integer::sum);
18+
freq.merge(cnt.get(number), 1, Integer::sum);
2119
}
22-
freq.merge(f, -1, Integer::sum);
23-
cnt.merge(number, -1, Integer::sum);
24-
freq.merge(f - 1, 1, Integer::sum);
2520
}
2621

2722
public boolean hasFrequency(int frequency) {

0 commit comments

Comments
(0)

AltStyle によって変換されたページ (->オリジナル) /