From 1140934f0389809c9ab744d21e1c271379acf299 Mon Sep 17 00:00:00 2001
From: yanglbme <szuyanglb@outlook.com>
Date: Thu, 20 Apr 2023 22:17:54 +0800
Subject: [PATCH] feat: add solutions to lc problem: No.0125
No.0125.Valid Palindrome
---
.../0100-0199/0125.Valid Palindrome/README.md | 200 +++++++-----------
.../0125.Valid Palindrome/README_EN.md | 187 ++++++----------
.../0125.Valid Palindrome/Solution.cpp | 16 +-
.../0125.Valid Palindrome/Solution.cs | 17 +-
.../0125.Valid Palindrome/Solution.go | 34 +--
.../0125.Valid Palindrome/Solution.java | 2 +-
.../0125.Valid Palindrome/Solution.js | 24 ++-
.../0125.Valid Palindrome/Solution.py | 13 ++
.../0125.Valid Palindrome/Solution.ts | 22 +-
9 files changed, 211 insertions(+), 304 deletions(-)
create mode 100644 solution/0100-0199/0125.Valid Palindrome/Solution.py
diff --git a/solution/0100-0199/0125.Valid Palindrome/README.md b/solution/0100-0199/0125.Valid Palindrome/README.md
index c53645aed491e..c7146421a7ba6 100644
--- a/solution/0100-0199/0125.Valid Palindrome/README.md
+++ b/solution/0100-0199/0125.Valid Palindrome/README.md
@@ -52,6 +52,19 @@
<!-- 这里可写通用的实现逻辑 -->
+**方法一：双指针**
+
+我们用双指针 $i$ 和 $j$ 分别指向字符串 $s$ 的两端，接下来循环以下过程，直至 $i \geq j$：
+
+1. 如果 $s[i]$ 不是字母或数字，指针 $i$ 右移一位，继续下一次循环；
+1. 如果 $s[j]$ 不是字母或数字，指针 $j$ 左移一位，继续下一次循环；
+1. 如果 $s[i]$ 和 $s[j]$ 的小写形式不相等，返回 `false`；
+1. 否则，指针 $i$ 右移一位，指针 $j$ 左移一位，继续下一次循环。
+
+循环结束，返回 `true`。
+
+时间复杂度 $O(n)$，其中 $n$ 是字符串 $s$ 的长度。空间复杂度 $O(1)$。
+
<!-- tabs:start -->
### **Python3**
@@ -70,8 +83,7 @@ class Solution:
elif s[i].lower() != s[j].lower():
return False
else:
- i += 1
- j -= 1
+ i, j = i + 1, j - 1
return True
```
@@ -88,7 +100,7 @@ class Solution {
++i;
} else if (!Character.isLetterOrDigit(s.charAt(j))) {
--j;
- } else if (Character.toUpperCase(s.charAt(i)) != Character.toUpperCase(s.charAt(j))) {
+ } else if (Character.toLowerCase(s.charAt(i)) != Character.toLowerCase(s.charAt(j))) {
return false;
} else {
++i;
@@ -108,43 +120,67 @@ public:
bool isPalindrome(string s) {
int i = 0, j = s.size() - 1;
while (i < j) {
- if (!isAlphaNum(s[i]))
+ if (!isalnum(s[i])) {
++i;
- else if (!isAlphaNum(s[j]))
+ } else if (!isalnum(s[j])) {
--j;
- else if ((s[i] + 32 - 'a') % 32 != (s[j] + 32 - 'a') % 32)
+ } else if (tolower(s[i]) != tolower(s[j])) {
return false;
- else {
+ } else {
++i;
--j;
}
}
return true;
}
-
-private:
- bool isAlphaNum(char& ch) {
- if (ch >= 'a' && ch <= 'z') return true;
- if (ch >= 'A' && ch <= 'Z') return true;
- if (ch >= '0' && ch <= '9') return true;
- return false;
- }
};
```
+### **Go**
+
+```go
+func isPalindrome(s string) bool {
+ i, j := 0, len(s)-1
+ for i < j {
+ if !isalnum(s[i]) {
+ i++
+ } else if !isalnum(s[j]) {
+ j--
+ } else if tolower(s[i]) != tolower(s[j]) {
+ return false
+ } else {
+ i, j = i+1, j-1
+ }
+ }
+ return true
+}
+
+func isalnum(ch byte) bool {
+ return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9')
+}
+
+func tolower(ch byte) byte {
+ if ch >= 'A' && ch <= 'Z' {
+ return ch + 32
+ }
+ return ch
+}
+```
+
### **C#**
```cs
-using System.Linq;
-
public class Solution {
public bool IsPalindrome(string s) {
- var chars = s.Where(ch => char.IsLetterOrDigit(ch)).Select(char.ToLower).ToList();
- var i = 0;
- var j = chars.Count - 1;
- for (; i < j; ++i, --j)
- {
- if (chars[i] != chars[j]) return false;
+ int i = 0, j = s.Length - 1;
+ while (i < j) {
+ if (!char.IsLetterOrDigit(s[i])) {
+ ++i;
+ } else if (!char.IsLetterOrDigit(s[j])) {
+ --j;
+ } else if (char.ToLower(s[i++]) != char.ToLower(s[j--])) {
+ return false;
+ }
}
return true;
}
@@ -159,57 +195,18 @@ public class Solution {
* @return {boolean}
*/
var isPalindrome = function (s) {
- let arr1 = [],
- arr2 = [];
- for (let i = 0; i < s.length; i++) {
- if (s[i] >= 'A' && s[i] <= 'Z') {
- arr1.push(s[i].toLowerCase());
- }
- if ((s[i] >= '0' && s[i] <= '9') || (s[i] >= 'a' && s[i] <= 'z')) {
- arr1.push(s[i]);
- }
- }
- arr2 = [...arr1];
- arr2.reverse();
- return arr1.join('') === arr2.join('');
-};
-```
-
-```js
-/**
- * @param {string} s
- * @return {boolean}
- */
-var isPalindrome = function (s) {
- function isNumOrAl(a) {
- if (
- (a >= 'A' && a <= 'Z') ||
- (a >= '0' && a <= '9') ||
- (a >= 'a' && a <= 'z')
- ) {
- return true;
- } else {
- return false;
- }
- }
-
- if (s.length === 0) {
- return true;
- }
- let i = 0,
- j = s.length - 1;
+ let i = 0;
+ let j = s.length - 1;
while (i < j) {
- while (i < j && !isNumOrAl(s[i])) {
- i++;
- }
- while (i < j && !isNumOrAl(s[j])) {
- j--;
- }
- if (s[i].toLowerCase() !== s[j].toLowerCase()) {
+ if (!/[a-zA-Z0-9]/.test(s[i])) {
+ ++i;
+ } else if (!/[a-zA-Z0-9]/.test(s[j])) {
+ --j;
+ } else if (s[i].toLowerCase() !== s[j].toLowerCase()) {
return false;
} else {
- i++;
- j--;
+ ++i;
+ --j;
}
}
return true;
@@ -220,36 +217,24 @@ var isPalindrome = function (s) {
```ts
function isPalindrome(s: string): boolean {
- let left: number = 0,
- right: number = s.length - 1;
- while (left < right) {
- let char1: string = s.charAt(left);
- let char2: string = s.charAt(right);
- if (!/[a-zA-Z0-9]/.test(char1)) {
- ++left;
- } else if (!/[a-zA-Z0-9]/.test(char2)) {
- --right;
- } else if (char1.toLocaleLowerCase() != char2.toLocaleLowerCase()) {
+ let i = 0;
+ let j = s.length - 1;
+ while (i < j) {
+ if (!/[a-zA-Z0-9]/.test(s[i])) {
+ ++i;
+ } else if (!/[a-zA-Z0-9]/.test(s[j])) {
+ --j;
+ } else if (s[i].toLowerCase() !== s[j].toLowerCase()) {
return false;
} else {
- ++left;
- --right;
+ ++i;
+ --j;
}
}
return true;
}
```
-```ts
-function isPalindrome(s: string): boolean {
- const isAlphanumeric = (c: string) => {
- return (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9');
- };
- const cs = s.toLocaleLowerCase().split('').filter(isAlphanumeric);
- return cs.join('') === cs.reverse().join('');
-}
-```
-
### **Rust**
```rust
@@ -279,35 +264,6 @@ impl Solution {
}
```
-### **Go**
-
-```go
-func isPalindrome(s string) bool {
- s = strings.ToLower(s)
- left, right := 0, len(s) - 1
- for left < right {
- for left < right && !verify(s[left]) {
- left++
- }
- for left < right && !verify(s[right]) {
- right--
- }
- if left < right {
- if s[left] != s[right] {
- return false
- }
- left++
- right--
- }
- }
- return true
-}
-
-func verify(ch byte) bool {
- return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9')
-}
-```
-
### **PHP**
```php
diff --git a/solution/0100-0199/0125.Valid Palindrome/README_EN.md b/solution/0100-0199/0125.Valid Palindrome/README_EN.md
index 38d356d454fb3..d474fe9e13764 100644
--- a/solution/0100-0199/0125.Valid Palindrome/README_EN.md
+++ b/solution/0100-0199/0125.Valid Palindrome/README_EN.md
@@ -60,8 +60,7 @@ class Solution:
elif s[i].lower() != s[j].lower():
return False
else:
- i += 1
- j -= 1
+ i, j = i + 1, j - 1
return True
```
@@ -76,7 +75,7 @@ class Solution {
++i;
} else if (!Character.isLetterOrDigit(s.charAt(j))) {
--j;
- } else if (Character.toUpperCase(s.charAt(i)) != Character.toUpperCase(s.charAt(j))) {
+ } else if (Character.toLowerCase(s.charAt(i)) != Character.toLowerCase(s.charAt(j))) {
return false;
} else {
++i;
@@ -96,43 +95,67 @@ public:
bool isPalindrome(string s) {
int i = 0, j = s.size() - 1;
while (i < j) {
- if (!isAlphaNum(s[i]))
+ if (!isalnum(s[i])) {
++i;
- else if (!isAlphaNum(s[j]))
+ } else if (!isalnum(s[j])) {
--j;
- else if ((s[i] + 32 - 'a') % 32 != (s[j] + 32 - 'a') % 32)
+ } else if (tolower(s[i]) != tolower(s[j])) {
return false;
- else {
+ } else {
++i;
--j;
}
}
return true;
}
-
-private:
- bool isAlphaNum(char& ch) {
- if (ch >= 'a' && ch <= 'z') return true;
- if (ch >= 'A' && ch <= 'Z') return true;
- if (ch >= '0' && ch <= '9') return true;
- return false;
- }
};
```
+### **Go**
+
+```go
+func isPalindrome(s string) bool {
+ i, j := 0, len(s)-1
+ for i < j {
+ if !isalnum(s[i]) {
+ i++
+ } else if !isalnum(s[j]) {
+ j--
+ } else if tolower(s[i]) != tolower(s[j]) {
+ return false
+ } else {
+ i, j = i+1, j-1
+ }
+ }
+ return true
+}
+
+func isalnum(ch byte) bool {
+ return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9')
+}
+
+func tolower(ch byte) byte {
+ if ch >= 'A' && ch <= 'Z' {
+ return ch + 32
+ }
+ return ch
+}
+```
+
### **C#**
```cs
-using System.Linq;
-
public class Solution {
public bool IsPalindrome(string s) {
- var chars = s.Where(ch => char.IsLetterOrDigit(ch)).Select(char.ToLower).ToList();
- var i = 0;
- var j = chars.Count - 1;
- for (; i < j; ++i, --j)
- {
- if (chars[i] != chars[j]) return false;
+ int i = 0, j = s.Length - 1;
+ while (i < j) {
+ if (!char.IsLetterOrDigit(s[i])) {
+ ++i;
+ } else if (!char.IsLetterOrDigit(s[j])) {
+ --j;
+ } else if (char.ToLower(s[i++]) != char.ToLower(s[j--])) {
+ return false;
+ }
}
return true;
}
@@ -147,57 +170,18 @@ public class Solution {
* @return {boolean}
*/
var isPalindrome = function (s) {
- let arr1 = [],
- arr2 = [];
- for (let i = 0; i < s.length; i++) {
- if (s[i] >= 'A' && s[i] <= 'Z') {
- arr1.push(s[i].toLowerCase());
- }
- if ((s[i] >= '0' && s[i] <= '9') || (s[i] >= 'a' && s[i] <= 'z')) {
- arr1.push(s[i]);
- }
- }
- arr2 = [...arr1];
- arr2.reverse();
- return arr1.join('') === arr2.join('');
-};
-```
-
-```js
-/**
- * @param {string} s
- * @return {boolean}
- */
-var isPalindrome = function (s) {
- function isNumOrAl(a) {
- if (
- (a >= 'A' && a <= 'Z') ||
- (a >= '0' && a <= '9') ||
- (a >= 'a' && a <= 'z')
- ) {
- return true;
- } else {
- return false;
- }
- }
-
- if (s.length === 0) {
- return true;
- }
- let i = 0,
- j = s.length - 1;
+ let i = 0;
+ let j = s.length - 1;
while (i < j) {
- while (i < j && !isNumOrAl(s[i])) {
- i++;
- }
- while (i < j && !isNumOrAl(s[j])) {
- j--;
- }
- if (s[i].toLowerCase() !== s[j].toLowerCase()) {
+ if (!/[a-zA-Z0-9]/.test(s[i])) {
+ ++i;
+ } else if (!/[a-zA-Z0-9]/.test(s[j])) {
+ --j;
+ } else if (s[i].toLowerCase() !== s[j].toLowerCase()) {
return false;
} else {
- i++;
- j--;
+ ++i;
+ --j;
}
}
return true;
@@ -208,36 +192,24 @@ var isPalindrome = function (s) {
```ts
function isPalindrome(s: string): boolean {
- let left: number = 0,
- right: number = s.length - 1;
- while (left < right) {
- let char1: string = s.charAt(left);
- let char2: string = s.charAt(right);
- if (!/[a-zA-Z0-9]/.test(char1)) {
- ++left;
- } else if (!/[a-zA-Z0-9]/.test(char2)) {
- --right;
- } else if (char1.toLocaleLowerCase() != char2.toLocaleLowerCase()) {
+ let i = 0;
+ let j = s.length - 1;
+ while (i < j) {
+ if (!/[a-zA-Z0-9]/.test(s[i])) {
+ ++i;
+ } else if (!/[a-zA-Z0-9]/.test(s[j])) {
+ --j;
+ } else if (s[i].toLowerCase() !== s[j].toLowerCase()) {
return false;
} else {
- ++left;
- --right;
+ ++i;
+ --j;
}
}
return true;
}
```
-```ts
-function isPalindrome(s: string): boolean {
- const isAlphanumeric = (c: string) => {
- return (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9');
- };
- const cs = s.toLocaleLowerCase().split('').filter(isAlphanumeric);
- return cs.join('') === cs.reverse().join('');
-}
-```
-
### **Rust**
```rust
@@ -267,35 +239,6 @@ impl Solution {
}
```
-### **Go**
-
-```go
-func isPalindrome(s string) bool {
- s = strings.ToLower(s)
- left, right := 0, len(s) - 1
- for left < right {
- for left < right && !verify(s[left]) {
- left++
- }
- for left < right && !verify(s[right]) {
- right--
- }
- if left < right {
- if s[left] != s[right] {
- return false
- }
- left++
- right--
- }
- }
- return true
-}
-
-func verify(ch byte) bool {
- return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9')
-}
-```
-
### **PHP**
```php
diff --git a/solution/0100-0199/0125.Valid Palindrome/Solution.cpp b/solution/0100-0199/0125.Valid Palindrome/Solution.cpp
index 242b625b1c58b..bbc2773e14d1e 100644
--- a/solution/0100-0199/0125.Valid Palindrome/Solution.cpp
+++ b/solution/0100-0199/0125.Valid Palindrome/Solution.cpp
@@ -3,25 +3,17 @@ class Solution {
bool isPalindrome(string s) {
int i = 0, j = s.size() - 1;
while (i < j) {
- if (!isAlphaNum(s[i]))
+ if (!isalnum(s[i])) {
++i;
- else if (!isAlphaNum(s[j]))
+ } else if (!isalnum(s[j])) {
--j;
- else if ((s[i] + 32 - 'a') % 32 != (s[j] + 32 - 'a') % 32)
+ } else if (tolower(s[i]) != tolower(s[j])) {
return false;
- else {
+ } else {
++i;
--j;
}
}
return true;
}
-
-private:
- bool isAlphaNum(char& ch) {
- if (ch >= 'a' && ch <= 'z') return true;
- if (ch >= 'A' && ch <= 'Z') return true;
- if (ch >= '0' && ch <= '9') return true;
- return false;
- }
};
\ No newline at end of file
diff --git a/solution/0100-0199/0125.Valid Palindrome/Solution.cs b/solution/0100-0199/0125.Valid Palindrome/Solution.cs
index dc2c4e9ad4223..594b7e02f1f13 100644
--- a/solution/0100-0199/0125.Valid Palindrome/Solution.cs
+++ b/solution/0100-0199/0125.Valid Palindrome/Solution.cs
@@ -1,13 +1,14 @@
-using System.Linq;
-
public class Solution {
public bool IsPalindrome(string s) {
- var chars = s.Where(ch => char.IsLetterOrDigit(ch)).Select(char.ToLower).ToList();
- var i = 0;
- var j = chars.Count - 1;
- for (; i < j; ++i, --j)
- {
- if (chars[i] != chars[j]) return false;
+ int i = 0, j = s.Length - 1;
+ while (i < j) {
+ if (!char.IsLetterOrDigit(s[i])) {
+ ++i;
+ } else if (!char.IsLetterOrDigit(s[j])) {
+ --j;
+ } else if (char.ToLower(s[i++]) != char.ToLower(s[j--])) {
+ return false;
+ }
}
return true;
}
diff --git a/solution/0100-0199/0125.Valid Palindrome/Solution.go b/solution/0100-0199/0125.Valid Palindrome/Solution.go
index 5b3ddec918777..47319af9e8632 100644
--- a/solution/0100-0199/0125.Valid Palindrome/Solution.go
+++ b/solution/0100-0199/0125.Valid Palindrome/Solution.go
@@ -1,24 +1,26 @@
func isPalindrome(s string) bool {
- s = strings.ToLower(s)
- left, right := 0, len(s) - 1
- for left < right {
- for left < right && !verify(s[left]) {
- left++
- }
- for left < right && !verify(s[right]) {
- right--
- }
- if left < right {
- if s[left] != s[right] {
- return false
- }
- left++
- right--
+ i, j := 0, len(s)-1
+ for i < j {
+ if !isalnum(s[i]) {
+ i++
+ } else if !isalnum(s[j]) {
+ j--
+ } else if tolower(s[i]) != tolower(s[j]) {
+ return false
+ } else {
+ i, j = i+1, j-1
}
}
return true
}
-func verify(ch byte) bool {
+func isalnum(ch byte) bool {
return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9')
+}
+
+func tolower(ch byte) byte {
+ if ch >= 'A' && ch <= 'Z' {
+ return ch + 32
+ }
+ return ch
}
\ No newline at end of file
diff --git a/solution/0100-0199/0125.Valid Palindrome/Solution.java b/solution/0100-0199/0125.Valid Palindrome/Solution.java
index 5df0ee2d50e76..1bf028c1f616c 100644
--- a/solution/0100-0199/0125.Valid Palindrome/Solution.java
+++ b/solution/0100-0199/0125.Valid Palindrome/Solution.java
@@ -6,7 +6,7 @@ public boolean isPalindrome(String s) {
++i;
} else if (!Character.isLetterOrDigit(s.charAt(j))) {
--j;
- } else if (Character.toUpperCase(s.charAt(i)) != Character.toUpperCase(s.charAt(j))) {
+ } else if (Character.toLowerCase(s.charAt(i)) != Character.toLowerCase(s.charAt(j))) {
return false;
} else {
++i;
diff --git a/solution/0100-0199/0125.Valid Palindrome/Solution.js b/solution/0100-0199/0125.Valid Palindrome/Solution.js
index f4d728dd21261..edde5786b0397 100644
--- a/solution/0100-0199/0125.Valid Palindrome/Solution.js
+++ b/solution/0100-0199/0125.Valid Palindrome/Solution.js
@@ -3,17 +3,19 @@
* @return {boolean}
*/
var isPalindrome = function (s) {
- let arr1 = [],
- arr2 = [];
- for (let i = 0; i < s.length; i++) {
- if (s[i] >= 'A' && s[i] <= 'Z') {
- arr1.push(s[i].toLowerCase());
- }
- if ((s[i] >= '0' && s[i] <= '9') || (s[i] >= 'a' && s[i] <= 'z')) {
- arr1.push(s[i]);
+ let i = 0;
+ let j = s.length - 1;
+ while (i < j) {
+ if (!/[a-zA-Z0-9]/.test(s[i])) {
+ ++i;
+ } else if (!/[a-zA-Z0-9]/.test(s[j])) {
+ --j;
+ } else if (s[i].toLowerCase() !== s[j].toLowerCase()) {
+ return false;
+ } else {
+ ++i;
+ --j;
}
}
- arr2 = [...arr1];
- arr2.reverse();
- return arr1.join('') === arr2.join('');
+ return true;
};
diff --git a/solution/0100-0199/0125.Valid Palindrome/Solution.py b/solution/0100-0199/0125.Valid Palindrome/Solution.py
new file mode 100644
index 0000000000000..73fac29a8c02d
--- /dev/null
+++ b/solution/0100-0199/0125.Valid Palindrome/Solution.py
@@ -0,0 +1,13 @@
+class Solution:
+ def isPalindrome(self, s: str) -> bool:
+ i, j = 0, len(s) - 1
+ while i < j:
+ if not s[i].isalnum():
+ i += 1
+ elif not s[j].isalnum():
+ j -= 1
+ elif s[i].lower() != s[j].lower():
+ return False
+ else:
+ i, j = i + 1, j - 1
+ return True
diff --git a/solution/0100-0199/0125.Valid Palindrome/Solution.ts b/solution/0100-0199/0125.Valid Palindrome/Solution.ts
index 4daab16efc9f7..b06244fa3c279 100644
--- a/solution/0100-0199/0125.Valid Palindrome/Solution.ts
+++ b/solution/0100-0199/0125.Valid Palindrome/Solution.ts
@@ -1,18 +1,16 @@
function isPalindrome(s: string): boolean {
- let left: number = 0,
- right: number = s.length - 1;
- while (left < right) {
- let char1: string = s.charAt(left);
- let char2: string = s.charAt(right);
- if (!/[a-zA-Z0-9]/.test(char1)) {
- ++left;
- } else if (!/[a-zA-Z0-9]/.test(char2)) {
- --right;
- } else if (char1.toLocaleLowerCase() != char2.toLocaleLowerCase()) {
+ let i = 0;
+ let j = s.length - 1;
+ while (i < j) {
+ if (!/[a-zA-Z0-9]/.test(s[i])) {
+ ++i;
+ } else if (!/[a-zA-Z0-9]/.test(s[j])) {
+ --j;
+ } else if (s[i].toLowerCase() !== s[j].toLowerCase()) {
return false;
} else {
- ++left;
- --right;
+ ++i;
+ --j;
}
}
return true;