feat: update lcci solutions: 01.04.Palindrome Permutation

Author: yanglbme

lcci/01.04.Palindrome Permutation/README.md

@@ -36,18 +36,16 @@
 ```python
 class Solution:
     def canPermutePalindrome(self, s: str) -> bool:
-        if s is None or len(s) < 2:
-            return True
-        cache = {}
-        for ch in s:
-            cache[ch] = 1 if cache.get(ch) is None else cache[ch] + 1
+        counter = collections.Counter()
+        for c in s:
+            counter[c] += 1
         cnt = 0
-        for k, v in cache.items():
-            if (v & 1) == 1:
+        for val in counter.values():
+            if (val & 1) == 1:
                 cnt += 1
             if cnt > 1:
                 return False
-        return cnt <= 1
+        return True
 ```
 
 ### **Java**
@@ -57,24 +55,21 @@ class Solution:
 ```java
 class Solution {
     public boolean canPermutePalindrome(String s) {
-        if (s == null || s.length() < 2) {
-            return true;
-        }
-        char[] chars = s.toCharArray();
         Map<Character, Integer> counter = new HashMap<>();
-        for (char ch : chars) {
-            counter.put(ch, counter.get(ch) == null ? 1 : counter.get(ch) + 1);
+        for (int i = 0, n = s.length(); i < n; ++i) {
+            char c = s.charAt(i);
+            counter.put(c, counter.getOrDefault(c, 0) + 1);
         }
         int cnt = 0;
-        for (Map.Entry<Character, Integer> entry : counter.entrySet()) {
-            if ((entry.getValue() & 1) == 1) {
+        for (int val : counter.values()) {
+            if ((val & 1) == 1) {
                 ++cnt;
             }
             if (cnt > 1) {
                 return false;
             }
         }
-        return cnt <= 1;
+        return true;
     }
 }
 ```

lcci/01.04.Palindrome Permutation/README_EN.md

@@ -27,43 +27,38 @@
 ```python
 class Solution:
     def canPermutePalindrome(self, s: str) -> bool:
-        if s is None or len(s) < 2:
-            return True
-        cache = {}
-        for ch in s:
-            cache[ch] = 1 if cache.get(ch) is None else cache[ch] + 1
+        counter = collections.Counter()
+        for c in s:
+            counter[c] += 1
         cnt = 0
-        for k, v in cache.items():
-            if (v & 1) == 1:
+        for val in counter.values():
+            if (val & 1) == 1:
                 cnt += 1
             if cnt > 1:
                 return False
-        return cnt <= 1
+        return True
 ```
 
 ### **Java**
 
 ```java
 class Solution {
     public boolean canPermutePalindrome(String s) {
-        if (s == null || s.length() < 2) {
-            return true;
-        }
-        char[] chars = s.toCharArray();
         Map<Character, Integer> counter = new HashMap<>();
-        for (char ch : chars) {
-            counter.put(ch, counter.get(ch) == null ? 1 : counter.get(ch) + 1);
+        for (int i = 0, n = s.length(); i < n; ++i) {
+            char c = s.charAt(i);
+            counter.put(c, counter.getOrDefault(c, 0) + 1);
         }
         int cnt = 0;
-        for (Map.Entry<Character, Integer> entry : counter.entrySet()) {
-            if ((entry.getValue() & 1) == 1) {
+        for (int val : counter.values()) {
+            if ((val & 1) == 1) {
                 ++cnt;
             }
             if (cnt > 1) {
                 return false;
             }
         }
-        return cnt <= 1;
+        return true;
     }
 }
 ```

lcci/01.04.Palindrome Permutation/Solution.java

@@ -1,22 +1,19 @@
 class Solution {
     public boolean canPermutePalindrome(String s) {
-        if (s == null || s.length() < 2) {
-            return true;
-        }
-        char[] chars = s.toCharArray();
         Map<Character, Integer> counter = new HashMap<>();
-        for (char ch : chars) {
-            counter.put(ch, counter.get(ch) == null ? 1 : counter.get(ch) + 1);
+        for (int i = 0, n = s.length(); i < n; ++i) {
+            char c = s.charAt(i);
+            counter.put(c, counter.getOrDefault(c, 0) + 1);
         }
         int cnt = 0;
-        for (Map.Entry<Character, Integer> entry : counter.entrySet()) {
-            if ((entry.getValue() & 1) == 1) {
+        for (int val : counter.values()) {
+            if ((val & 1) == 1) {
                 ++cnt;
             }
             if (cnt > 1) {
                 return false;
             }
         }
-        return cnt <= 1;
+        return true;
     }
 }

lcci/01.04.Palindrome Permutation/Solution.py

@@ -0,0 +1,12 @@
+class Solution:
+    def canPermutePalindrome(self, s: str) -> bool:
+        counter = collections.Counter()
+        for c in s:
+            counter[c] += 1
+        cnt = 0
+        for val in counter.values():
+            if (val & 1) == 1:
+                cnt += 1
+            if cnt > 1:
+                return False
+        return True