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feat: update solutions to lc problem: No.1456 (#2554)
No.1456.Maximum Number of Vowels in a Substring of Given Length
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‎solution/1400-1499/1456.Maximum Number of Vowels in a Substring of Given Length/README.md

+48-52
Original file line numberDiff line numberDiff line change
@@ -64,43 +64,45 @@
6464

6565
### 方法一：滑动窗口
6666

67-
找出所有窗口为 $k$ 中的元音字母数目，并记录最大值。
67+
我们首先统计前 $k$ 个字符中元音字母的个数，记为 $cnt$，初始化答案 $ans$ 为 $cnt$。
6868

69-
时间复杂度 $O(n)$，空间复杂度 $O(1)$。
69+
然后我们从 $k$ 开始遍历字符串，每次遍历时，我们将当前字符加入窗口，如果当前字符是元音字母，则 $cnt$ 加一；将窗口第一个字符移出窗口，如果移除的字符是元音字母，则 $cnt$ 减一。然后，我们更新答案 $ans = \max(ans, cnt)$。
70+
71+
遍历结束后，返回答案即可。
72+
73+
时间复杂度 $O(n)$，其中 $n$ 为字符串 $s$ 的长度。空间复杂度 $O(1)$。
7074

7175
<!-- tabs:start -->
7276

7377
```python
7478
class Solution:
7579
def maxVowels(self, s: str, k: int) -> int:
76-
vowels = set('aeiou')
77-
t = sum(c in vowels for c in s[:k])
78-
ans = t
80+
vowels = set("aeiou")
81+
ans = cnt = sum(c in vowels for c in s[:k])
7982
for i in range(k, len(s)):
80-
t += s[i] in vowels
81-
t -= s[i - k] in vowels
82-
ans = max(ans, t)
83+
cnt += int(s[i] in vowels) - int(s[i - k] in vowels)
84+
ans = max(ans, cnt)
8385
return ans
8486
```
8587

8688
```java
8789
class Solution {
8890
public int maxVowels(String s, int k) {
89-
int t = 0, n = s.length();
91+
int cnt = 0;
9092
for (int i = 0; i < k; ++i) {
9193
if (isVowel(s.charAt(i))) {
92-
++t;
94+
++cnt;
9395
}
9496
}
95-
int ans = t;
96-
for (int i = k; i < n; ++i) {
97+
int ans = cnt;
98+
for (int i = k; i < s.length(); ++i) {
9799
if (isVowel(s.charAt(i))) {
98-
++t;
100+
++cnt;
99101
}
100102
if (isVowel(s.charAt(i - k))) {
101-
--t;
103+
--cnt;
102104
}
103-
ans = Math.max(ans, t);
105+
ans = Math.max(ans, cnt);
104106
}
105107
return ans;
106108
}
@@ -115,20 +117,17 @@ class Solution {
115117
class Solution {
116118
public:
117119
int maxVowels(string s, int k) {
118-
int t = 0, n = s.size();
119-
for (int i = 0; i < k; ++i) t += isVowel(s[i]);
120-
int ans = t;
121-
for (int i = k; i < n; ++i) {
122-
t += isVowel(s[i]);
123-
t -= isVowel(s[i - k]);
124-
ans = max(ans, t);
120+
auto isVowel = [](char c) {
121+
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
122+
};
123+
int cnt = count_if(s.begin(), s.begin() + k, isVowel);
124+
int ans = cnt;
125+
for (int i = k; i < s.size(); ++i) {
126+
cnt += isVowel(s[i]) - isVowel(s[i - k]);
127+
ans = max(ans, cnt);
125128
}
126129
return ans;
127130
}
128-
129-
bool isVowel(char c) {
130-
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
131-
}
132131
};
133132
```
134133
@@ -137,46 +136,44 @@ func maxVowels(s string, k int) int {
137136
isVowel := func(c byte) bool {
138137
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u'
139138
}
140-
t := 0
139+
cnt := 0
141140
for i := 0; i < k; i++ {
142141
if isVowel(s[i]) {
143-
t++
142+
cnt++
144143
}
145144
}
146-
ans := t
145+
ans := cnt
147146
for i := k; i < len(s); i++ {
148-
if isVowel(s[i]) {
149-
t++
150-
}
151147
if isVowel(s[i-k]) {
152-
t--
148+
cnt--
149+
}
150+
if isVowel(s[i]) {
151+
cnt++
153152
}
154-
ans = max(ans, t)
153+
ans = max(ans, cnt)
155154
}
156155
return ans
157156
}
158157
```
159158

160159
```ts
161160
function maxVowels(s: string, k: number): number {
162-
function isVowel(c) {
163-
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
164-
}
165-
let t = 0;
166-
for (let i = 0; i < k; ++i) {
167-
if (isVowel(s.charAt(i))) {
168-
t++;
161+
const isVowel = (c: string) => ['a', 'e', 'i', 'o', 'u'].includes(c);
162+
let cnt = 0;
163+
for (let i = 0; i < k; i++) {
164+
if (isVowel(s[i])) {
165+
cnt++;
169166
}
170167
}
171-
let ans = t;
172-
for (let i = k; i < s.length; ++i) {
173-
if (isVowel(s.charAt(i))) {
174-
t++;
168+
let ans = cnt;
169+
for (let i = k; i < s.length; i++) {
170+
if (isVowel(s[i])) {
171+
cnt++;
175172
}
176-
if (isVowel(s.charAt(i - k))) {
177-
t--;
173+
if (isVowel(s[i - k])) {
174+
cnt--;
178175
}
179-
ans = Math.max(ans, t);
176+
ans = Math.max(ans, cnt);
180177
}
181178
return ans;
182179
}
@@ -194,23 +191,22 @@ class Solution {
194191
}
195192
function maxVowels($s, $k) {
196193
$cnt = 0;
197-
$rs = 0;
198194
for ($i = 0; $i < $k; $i++) {
199195
if ($this->isVowel($s[$i])) {
200196
$cnt++;
201197
}
202198
}
203-
$rs = $cnt;
199+
$ans = $cnt;
204200
for ($j = $k; $j < strlen($s); $j++) {
205201
if ($this->isVowel($s[$j - $k])) {
206202
$cnt--;
207203
}
208204
if ($this->isVowel($s[$j])) {
209205
$cnt++;
210206
}
211-
$rs = max($rs, $cnt);
207+
$ans = max($ans, $cnt);
212208
}
213-
return $rs;
209+
return $ans;
214210
}
215211
}
216212
```

‎solution/1400-1499/1456.Maximum Number of Vowels in a Substring of Given Length/README_EN.md

+51-51
Original file line numberDiff line numberDiff line change
@@ -46,41 +46,47 @@
4646

4747
## Solutions
4848

49-
### Solution 1
49+
### Solution 1: Sliding Window
50+
51+
First, we count the number of vowels in the first $k$ characters, denoted as $cnt$, and initialize the answer $ans$ as $cnt$.
52+
53+
Then we start traversing the string from $k$. For each iteration, we add the current character to the window. If the current character is a vowel, we increment $cnt$. We remove the first character from the window. If the removed character is a vowel, we decrement $cnt$. Then, we update the answer $ans = \max(ans, cnt)$.
54+
55+
After the traversal, we return the answer.
56+
57+
The time complexity is $O(n)$, where $n$ is the length of the string $s$. The space complexity is $O(1)$.
5058

5159
<!-- tabs:start -->
5260

5361
```python
5462
class Solution:
5563
def maxVowels(self, s: str, k: int) -> int:
56-
vowels = set('aeiou')
57-
t = sum(c in vowels for c in s[:k])
58-
ans = t
64+
vowels = set("aeiou")
65+
ans = cnt = sum(c in vowels for c in s[:k])
5966
for i in range(k, len(s)):
60-
t += s[i] in vowels
61-
t -= s[i - k] in vowels
62-
ans = max(ans, t)
67+
cnt += int(s[i] in vowels) - int(s[i - k] in vowels)
68+
ans = max(ans, cnt)
6369
return ans
6470
```
6571

6672
```java
6773
class Solution {
6874
public int maxVowels(String s, int k) {
69-
int t = 0, n = s.length();
75+
int cnt = 0;
7076
for (int i = 0; i < k; ++i) {
7177
if (isVowel(s.charAt(i))) {
72-
++t;
78+
++cnt;
7379
}
7480
}
75-
int ans = t;
76-
for (int i = k; i < n; ++i) {
81+
int ans = cnt;
82+
for (int i = k; i < s.length(); ++i) {
7783
if (isVowel(s.charAt(i))) {
78-
++t;
84+
++cnt;
7985
}
8086
if (isVowel(s.charAt(i - k))) {
81-
--t;
87+
--cnt;
8288
}
83-
ans = Math.max(ans, t);
89+
ans = Math.max(ans, cnt);
8490
}
8591
return ans;
8692
}
@@ -95,20 +101,17 @@ class Solution {
95101
class Solution {
96102
public:
97103
int maxVowels(string s, int k) {
98-
int t = 0, n = s.size();
99-
for (int i = 0; i < k; ++i) t += isVowel(s[i]);
100-
int ans = t;
101-
for (int i = k; i < n; ++i) {
102-
t += isVowel(s[i]);
103-
t -= isVowel(s[i - k]);
104-
ans = max(ans, t);
104+
auto isVowel = [](char c) {
105+
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
106+
};
107+
int cnt = count_if(s.begin(), s.begin() + k, isVowel);
108+
int ans = cnt;
109+
for (int i = k; i < s.size(); ++i) {
110+
cnt += isVowel(s[i]) - isVowel(s[i - k]);
111+
ans = max(ans, cnt);
105112
}
106113
return ans;
107114
}
108-
109-
bool isVowel(char c) {
110-
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
111-
}
112115
};
113116
```
114117
@@ -117,46 +120,44 @@ func maxVowels(s string, k int) int {
117120
isVowel := func(c byte) bool {
118121
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u'
119122
}
120-
t := 0
123+
cnt := 0
121124
for i := 0; i < k; i++ {
122125
if isVowel(s[i]) {
123-
t++
126+
cnt++
124127
}
125128
}
126-
ans := t
129+
ans := cnt
127130
for i := k; i < len(s); i++ {
128-
if isVowel(s[i]) {
129-
t++
130-
}
131131
if isVowel(s[i-k]) {
132-
t--
132+
cnt--
133+
}
134+
if isVowel(s[i]) {
135+
cnt++
133136
}
134-
ans = max(ans, t)
137+
ans = max(ans, cnt)
135138
}
136139
return ans
137140
}
138141
```
139142

140143
```ts
141144
function maxVowels(s: string, k: number): number {
142-
function isVowel(c) {
143-
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
144-
}
145-
let t = 0;
146-
for (let i = 0; i < k; ++i) {
147-
if (isVowel(s.charAt(i))) {
148-
t++;
145+
const isVowel = (c: string) => ['a', 'e', 'i', 'o', 'u'].includes(c);
146+
let cnt = 0;
147+
for (let i = 0; i < k; i++) {
148+
if (isVowel(s[i])) {
149+
cnt++;
149150
}
150151
}
151-
let ans = t;
152-
for (let i = k; i < s.length; ++i) {
153-
if (isVowel(s.charAt(i))) {
154-
t++;
152+
let ans = cnt;
153+
for (let i = k; i < s.length; i++) {
154+
if (isVowel(s[i])) {
155+
cnt++;
155156
}
156-
if (isVowel(s.charAt(i - k))) {
157-
t--;
157+
if (isVowel(s[i - k])) {
158+
cnt--;
158159
}
159-
ans = Math.max(ans, t);
160+
ans = Math.max(ans, cnt);
160161
}
161162
return ans;
162163
}
@@ -174,23 +175,22 @@ class Solution {
174175
}
175176
function maxVowels($s, $k) {
176177
$cnt = 0;
177-
$rs = 0;
178178
for ($i = 0; $i < $k; $i++) {
179179
if ($this->isVowel($s[$i])) {
180180
$cnt++;
181181
}
182182
}
183-
$rs = $cnt;
183+
$ans = $cnt;
184184
for ($j = $k; $j < strlen($s); $j++) {
185185
if ($this->isVowel($s[$j - $k])) {
186186
$cnt--;
187187
}
188188
if ($this->isVowel($s[$j])) {
189189
$cnt++;
190190
}
191-
$rs = max($rs, $cnt);
191+
$ans = max($ans, $cnt);
192192
}
193-
return $rs;
193+
return $ans;
194194
}
195195
}
196196
```

‎solution/1400-1499/1456.Maximum Number of Vowels in a Substring of Given Length/Solution.cpp

+8-11
Original file line numberDiff line numberDiff line change
@@ -1,18 +1,15 @@
11
class Solution {
22
public:
33
int maxVowels(string s, int k) {
4-
int t = 0, n = s.size();
5-
for (int i = 0; i < k; ++i) t += isVowel(s[i]);
6-
int ans = t;
7-
for (int i = k; i < n; ++i) {
8-
t += isVowel(s[i]);
9-
t -= isVowel(s[i - k]);
10-
ans = max(ans, t);
4+
auto isVowel = [](char c) {
5+
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
6+
};
7+
int cnt = count_if(s.begin(), s.begin() + k, isVowel);
8+
int ans = cnt;
9+
for (int i = k; i < s.size(); ++i) {
10+
cnt += isVowel(s[i]) - isVowel(s[i - k]);
11+
ans = max(ans, cnt);
1112
}
1213
return ans;
1314
}
14-
15-
bool isVowel(char c) {
16-
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
17-
}
1815
};

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