From 60077083b7b7b7b5aa6dcdf61f335b86a6c106e6 Mon Sep 17 00:00:00 2001
From: Rishav Ranjan <rishavranjan943@gmail.com>
Date: Tue, 3 Oct 2023 02:49:48 +0530
Subject: [PATCH 1/3] checkpermutation in o(1)

---
 1-Array-And-String/CheckPermutation.cpp | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/1-Array-And-String/CheckPermutation.cpp b/1-Array-And-String/CheckPermutation.cpp
index 86f9cb1..99ee062 100644
--- a/1-Array-And-String/CheckPermutation.cpp
+++ b/1-Array-And-String/CheckPermutation.cpp
@@ -18,18 +18,14 @@ bool checkPermutation( string string1, string string2 ) {
   if( string1.length() != string2.length() ) {
     return false;
   }
-  int charMap[128] = {0};
-  for( int i=0; i < string1.length(); i++ ) {
-    charMap[ string1[ i ] ]++;
+  int xorValue=0;
+  for(char ch : string1){
+    xorValue^=ch;
   }
-
-  for( int i=0; i < string2.length(); i++ ) {
-    if( charMap[ string2[ i ] ] == 0 ) {
-      return false;
-    }
-    charMap[ string2[ i ] ]--;
+  for(char ch : string2){
+    xorValue^=ch;
   }
-  return true;
+  return xorValue==0;
 }
 
 bool checkPermutationUsingSorting( string input1, string input2 ) {

From d2f3308278d66393ad4ebc4571d15908b882c2c1 Mon Sep 17 00:00:00 2001
From: Rishav Ranjan <rishavranjan943@gmail.com>
Date: Tue, 3 Oct 2023 02:59:13 +0530
Subject: [PATCH 2/3] duplicate in o(1) space and o(n^2) time

---
 1-Array-And-String/IsUnique.cpp | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/1-Array-And-String/IsUnique.cpp b/1-Array-And-String/IsUnique.cpp
index fb29b6a..10c7cc2 100644
--- a/1-Array-And-String/IsUnique.cpp
+++ b/1-Array-And-String/IsUnique.cpp
@@ -20,12 +20,11 @@ bool isDupUsingHashTable( string input ) {
     return true;
   }
 
-  bool map[ 128 ] = { false };
-  for( int i=0; i <  input.length(); i++ ) {
-    if( map[ input[ i ] ] == true )
-      return true;
-    else
-      map[ input[ i ] ]= true;
+  for(int i=0;i<input.length();i++){
+    for(int j=i+1;j<input.length();j++){
+      if(input[i]==input[j])
+        return true;
+    }
   }
   return false;
 }

From 963aa247f72a5f65cac99845269b8101b39e8bc4 Mon Sep 17 00:00:00 2001
From: Rishav Ranjan <rishavranjan943@gmail.com>
Date: Tue, 3 Oct 2023 03:07:05 +0530
Subject: [PATCH 3/3] o(n) time

---
 1-Array-And-String/PalindromePermutation.cpp | 36 +++++++-------------
 1 file changed, 13 insertions(+), 23 deletions(-)

diff --git a/1-Array-And-String/PalindromePermutation.cpp b/1-Array-And-String/PalindromePermutation.cpp
index 55199fe..e348b8e 100644
--- a/1-Array-And-String/PalindromePermutation.cpp
+++ b/1-Array-And-String/PalindromePermutation.cpp
@@ -11,33 +11,23 @@
 using namespace std;
 
 bool canFormPalindrome( string input ) {
-  int charFreqCount[ 26 ] = {0};
+   int charFreqCount[26] = {0};
 
-  int charCount = 0;
-  for( int i = 0; i < input.length(); i++ ) {
-    if( input[ i ] == ' ' ) {
-      continue;
+    for (char c : input) {
+        if (isspace(c)) continue;
+        if (isalpha(c)) {
+            charFreqCount[tolower(c) - 'a']++;
+        }
     }
-    if( 'a' <= input[ i ] &&  input[ i ] <= 'z' ) {
-      charFreqCount[ input[ i ] - 'a' ]++;
-      charCount++;
-      continue;
+
+    int oddCount = 0;
+    for (int i = 0; i < 26; i++) {
+        if (charFreqCount[i] % 2 != 0) {
+            oddCount++;
+        }
     }
-    if( 'A' <= input[ i ] &&  input[ i ] <= 'Z' ) {
-      charFreqCount[ input[ i ] - 'A' ]++;
-      charCount++;
-    }    
-  }
-  
-  int oddCount = 0;
-  for( int i=0; i < 26; i++ ) {
-    if( charFreqCount[ i ] % 2 != 0 )
-      oddCount++;
-  }
 
-  if( oddCount == 0 && charCount % 2 == 0 ) {
-    // when char count is even but oddCount is zero.
-    return true;
+    return oddCount <= 1;
   }
   
   if( charCount % 2 != 0 && oddCount == 1 ) {