[Interview] Check Permutation

[Interview] Check Permutation

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Question:
Given 2 Strings, write a method to decide if one is a permutation of the other.

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Idea 1: 
count the number of each character in first string and check if the number of each character in the 2nd string is the same as the 1st string.

Solution 1：

public class Solution{
 boolean checker(String str1, String str2)
 {
  if (str1.length() != str2.length()) return false;
  
  int[] helper = new int[256];
  
  for(int i = 0 ; i<str1.length();i++)
  {
   int index = str1.charAt(i);
   helper[index]++;
  }
  
  for(int i = 0 ; i<str2.length();i++)
  {
   int index = str2.charAt(i);
   helper[index]--;
   if(helper[index]<0) return false;
  }
  
  return true;
 }
}

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Idea 2: 
Sort the strings and check if they are same

Solution 2：

public class Solution{
 boolean checker2(String str1, String str2)
 {
  if (str1.length() != str2.length()) return false;
  return sort(str1).equals(sort(str2));
 }
 
 String sort(String str)
 {
  char[] c = str.toCharArray();
  Arrays.sort(c);
  return new String(c);
  
 }

}

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Video Explanation