leetcode

Author: ayoubzulfiqar

LongestPalindrome/longest_palindrome.dart

@@ -0,0 +1,147 @@
+/*
+
+-* 409. Longest Palindrome *-
+
+Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.
+
+Letters are case sensitive, for example, "Aa" is not considered a palindrome here.
+
+ 
+
+Example 1:
+
+Input: s = "abccccdd"
+Output: 7
+Explanation: One longest palindrome that can be built is "dccaccd", whose length is 7.
+Example 2:
+
+Input: s = "a"
+Output: 1
+Explanation: The longest palindrome that can be built is "a", whose length is 1.
+ 
+
+Constraints:
+
+1 <= s.length <= 2000
+s consists of lowercase and/or uppercase English letters only.
+
+*/
+
+class Solution {
+  int longestPalindrome(String s) {
+    Map<String, int> frequency = {};
+    int length = 0;
+
+    // Count the frequency of each letter
+    for (int i = 0; i < s.length; i++) {
+      String char = s[i];
+      frequency[char] = (frequency[char] ?? 0) + 1;
+    }
+
+    // Iterate through the frequency counts
+    frequency.values.forEach((count) {
+      if (count % 2 == 0) {
+        length += count;
+      } else {
+        length += count - 1;
+      }
+    });
+
+    // Check for remaining letters with odd counts
+    if (length < s.length) {
+      length += 1;
+    }
+
+    return length;
+  }
+}
+
+class B {
+  int longestPalindrome(String s) {
+    List<int> count = List<int>.filled(256, 0);
+    int odds = 0;
+
+    for (int i = 0; i < s.length; i++) {
+      int char = s.codeUnitAt(i);
+      count[char]++;
+      if (count[char] % 2 == 1) {
+        odds++;
+      } else {
+        odds--;
+      }
+    }
+
+    return s.length - odds + boolToInt(odds > 0);
+  }
+
+  int boolToInt(bool b) {
+    return b ? 1 : 0;
+  }
+}
+
+class C {
+  int longestPalindrome(String s) {
+    int dp = s.runes.fold(0, (int acc, int x) {
+      acc ^= 1 << (x - 65);
+      return acc;
+    });
+
+    return s.length - countSetBits(dp) + (dp != 0 ? 1 : 0);
+  }
+
+  int countSetBits(int n) {
+    int count = 0;
+    while (n != 0) {
+      count += n & 1;
+      n >>= 1;
+    }
+    return count;
+  }
+}
+
+class BitSet {
+  int _value;
+
+  BitSet() : _value = 0;
+
+  void flip(int k) {
+    _value ^= (1 << k);
+  }
+
+  bool get(int k) {
+    return ((_value >> k) & 1) == 1;
+  }
+}
+
+class E {
+  int longestPalindrome(String s) {
+    if (s.isEmpty) {
+      return 0;
+    }
+
+    BitSet bitSet = BitSet();
+    int ans = 0;
+
+    for (int ch in s.runes) {
+      int pos = 0;
+
+      if (ch >= 65 && ch <= 90) {
+        pos = ch - 65 + 26;
+      } else {
+        pos = ch - 97;
+      }
+
+      if (bitSet.get(pos)) {
+        ans += 2;
+      }
+
+      bitSet.flip(pos);
+    }
+
+    return min(ans + 1, s.length);
+  }
+
+  int min(int a, int b) {
+    return a < b ? a : b;
+  }
+}

LongestPalindrome/longest_palindrome.go

@@ -0,0 +1,53 @@
+package main
+
+func longestPalindrome1(s string) int {
+	frequency := make(map[string]int)
+	length := 0
+
+	// Count the frequency of each letter
+	for i := 0; i < len(s); i++ {
+		char := string(s[i])
+		frequency[char] = frequency[char] + 1
+	}
+
+	// Iterate through the frequency counts
+	for _, count := range frequency {
+		if count%2 == 0 {
+			length += count
+		} else {
+			length += count - 1
+		}
+	}
+
+	// Check for remaining letters with odd counts
+	if length < len(s) {
+		length += 1
+	}
+
+	return length
+}
+
+// type Solution struct{}
+
+func longestPalindrome(str string) int {
+	count := make([]int, 256)
+	odds := 0
+
+	for _, char := range str {
+		count[char]++
+		if count[char]&1 == 1 {
+			odds++
+		} else {
+			odds--
+		}
+	}
+
+	return len(str) - odds + boolToInt(odds > 0)
+}
+
+func boolToInt(b bool) int {
+	if b {
+		return 1
+	}
+	return 0
+}

LongestPalindrome/longest_palindrome.md

@@ -223,6 +223,7 @@ This repo contain leetcode solution using DART and GO programming language. Most
 - [**1232.** Check If It Is a Straight Line](CheckIfItIsAStraightLine/check_if_it_is_a_straight_line.dart)
 - [**405.** Convert a Number to Hexadecimal](ConvertANumberToHexadecimal/convert_a_number_to_hexadecimal.dart)
 - [**1502.** Can Make Arithmetic Progression From Sequence](CanMakeArithmeticProgressionFromSequence/can_make_arithmetic_progression_from_sequence.dart)
+- [**409.** Longest Palindrome](LongestPalindrome/longest_palindrome.dart)
 
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