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 a4dacea

Browse files
feat: add solutions to lcof2 problem: No.018 (doocs#1475)
No.018.验证回文串II
1 parent bb9b599 commit a4dacea

File tree

5 files changed

+89
-42
lines changed

5 files changed

+89
-42
lines changed

‎lcof2/剑指 Offer II 018. 有效的回文/README.md‎

Lines changed: 37 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -41,6 +41,12 @@
4141

4242
<!-- 这里可写通用的实现逻辑 -->
4343

44+
**方法一:双指针**
45+
46+
我们定义两个指针 $i$ 和 $j,ドル初始时分别指向字符串的首尾位置,每次判断两个指针指向的字符是否为数字或字母,如果两个指针指向的字符都为数字或字母时,判断两个指针指向的字符是否相同(忽略大小写),如果不相同则返回 `false`,否则将两个指针向中间移动一位,直到两个指针相遇时返回 `true`。
47+
48+
时间复杂度 $O(n),ドル其中 $n$ 是字符串的长度。空间复杂度 $O(1)$。
49+
4450
<!-- tabs:start -->
4551

4652
### **Python3**
@@ -58,8 +64,7 @@ class Solution:
5864
j -= 1
5965
if s[i].lower() != s[j].lower():
6066
return False
61-
i += 1
62-
j -= 1
67+
i, j = i + 1, j - 1
6368
return True
6469
```
6570

@@ -73,22 +78,47 @@ class Solution {
7378
int i = 0, j = s.length() - 1;
7479
while (i < j) {
7580
while (i < j && !Character.isLetterOrDigit(s.charAt(i))) {
76-
i++;
81+
++i;
7782
}
7883
while (i < j && !Character.isLetterOrDigit(s.charAt(j))) {
79-
j--;
84+
--j;
8085
}
8186
if (Character.toLowerCase(s.charAt(i)) != Character.toLowerCase(s.charAt(j))) {
8287
return false;
8388
}
84-
i++;
85-
j--;
89+
++i;
90+
--j;
8691
}
8792
return true;
8893
}
8994
}
9095
```
9196

97+
### **C++**
98+
99+
```cpp
100+
class Solution {
101+
public:
102+
bool isPalindrome(string s) {
103+
int i = 0, j = s.size() - 1;
104+
while (i < j) {
105+
while (i < j && !isalnum(s[i])) {
106+
++i;
107+
}
108+
while (i < j && !isalnum(s[j])) {
109+
--j;
110+
}
111+
if (tolower(s[i]) != tolower(s[j])) {
112+
return false;
113+
}
114+
++i;
115+
--j;
116+
}
117+
return true;
118+
}
119+
};
120+
```
121+
92122
### **Go**
93123
94124
```go
@@ -104,8 +134,7 @@ func isPalindrome(s string) bool {
104134
if tolower(s[i]) != tolower(s[j]) {
105135
return false
106136
}
107-
i++
108-
j--
137+
i, j = i+1, j-1
109138
}
110139
return true
111140
}
Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,20 @@
1+
class Solution {
2+
public:
3+
bool isPalindrome(string s) {
4+
int i = 0, j = s.size() - 1;
5+
while (i < j) {
6+
while (i < j && !isalnum(s[i])) {
7+
++i;
8+
}
9+
while (i < j && !isalnum(s[j])) {
10+
--j;
11+
}
12+
if (tolower(s[i]) != tolower(s[j])) {
13+
return false;
14+
}
15+
++i;
16+
--j;
17+
}
18+
return true;
19+
}
20+
};

‎lcof2/剑指 Offer II 018. 有效的回文/Solution.go‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -10,8 +10,7 @@ func isPalindrome(s string) bool {
1010
if tolower(s[i]) != tolower(s[j]) {
1111
return false
1212
}
13-
i++
14-
j--
13+
i, j = i+1, j-1
1514
}
1615
return true
1716
}
Lines changed: 19 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -1,19 +1,19 @@
1-
class Solution {
2-
public boolean isPalindrome(String s) {
3-
int i = 0, j = s.length() - 1;
4-
while (i < j) {
5-
while (i < j && !Character.isLetterOrDigit(s.charAt(i))) {
6-
i++;
7-
}
8-
while (i < j && !Character.isLetterOrDigit(s.charAt(j))) {
9-
j--;
10-
}
11-
if (Character.toLowerCase(s.charAt(i)) != Character.toLowerCase(s.charAt(j))) {
12-
return false;
13-
}
14-
i++;
15-
j--;
16-
}
17-
return true;
18-
}
19-
}
1+
class Solution {
2+
public boolean isPalindrome(String s) {
3+
int i = 0, j = s.length() - 1;
4+
while (i < j) {
5+
while (i < j && !Character.isLetterOrDigit(s.charAt(i))) {
6+
++i;
7+
}
8+
while (i < j && !Character.isLetterOrDigit(s.charAt(j))) {
9+
--j;
10+
}
11+
if (Character.toLowerCase(s.charAt(i)) != Character.toLowerCase(s.charAt(j))) {
12+
return false;
13+
}
14+
++i;
15+
--j;
16+
}
17+
return true;
18+
}
19+
}
Lines changed: 12 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -1,13 +1,12 @@
1-
class Solution:
2-
def isPalindrome(self, s: str) -> bool:
3-
i, j = 0, len(s) - 1
4-
while i < j:
5-
while i < j and not s[i].isalnum():
6-
i += 1
7-
while i < j and not s[j].isalnum():
8-
j -= 1
9-
if s[i].lower() != s[j].lower():
10-
return False
11-
i += 1
12-
j -= 1
13-
return True
1+
class Solution:
2+
def isPalindrome(self, s: str) -> bool:
3+
i, j = 0, len(s) - 1
4+
while i < j:
5+
while i < j and not s[i].isalnum():
6+
i += 1
7+
while i < j and not s[j].isalnum():
8+
j -= 1
9+
if s[i].lower() != s[j].lower():
10+
return False
11+
i, j = i + 1, j - 1
12+
return True

0 commit comments

Comments
(0)

AltStyle によって変換されたページ (->オリジナル) /