# Compare two strings considering only alphanumeric characters

Given two strings that can contain lower and uppercase alphabets, numbers and special characters like dots, blank spaces, commas, etc. Compare both strings considering only alphanumeric characters([a-b], [A-B] and [0-9]) if they are equal or not. For example, strings “Ram, Shyam” and “Ram-Shyam” both are the same and also “/.’;[]” and “@# >” are same.

Examples:

```Input: str1 = "Ram, Shyam", str2 = " Ram - Shyam."
Output: Equal
Explanation:
if we ignore all characters
except alphanumeric characters
then strings will be,
str1 = "RamShyam" and str2 = "RamShyam".
Therefore both strings are equal.

Input : str1 = "aaa123", str2 = "@aaa-12-3"
Output : Equal

Input : str1 = "abc123", str2 = "123abc"
Output : Unequal
Explanation:
In this, str1 = "abc123" and str2 = "123abc".
Therefore both strings are not equal.```

Since we have to compare only alphanumeric characters therefore whenever any other character is found simply ignore it by increasing iterator pointer. For doing it simply take two integer variables i and j and initialize them by 0. Now run a loop to compare each and every character of both strings. Compare one by one if the character is alphanumeric otherwise increase the value of i or j by one.

Below is the implementation of the above approach:

## C++

 `#include ` `using` `namespace` `std;`   `// Function to check alphanumeric equality of both strings` `bool` `CompareAlphanumeric(string& str1, string& str2)` `{` `    ``// variable declaration` `    ``int` `i, j;` `    ``i = 0;` `    ``j = 0;`   `    ``// Length of first string` `    ``int` `len1 = str1.size();`   `    ``// Length of second string` `    ``int` `len2 = str2.size();`   `    ``// To check each and every characters of both string` `    ``while` `(i <= len1 && j <= len2) {`   `        ``// If the current character of the first string is not an` `        ``// alphanumeric character, increase the pointer i` `        ``while` `(i < len1` `               ``&& (!((str1[i] >= ``'a'` `&& str1[i] <= ``'z'``)` `                     ``|| (str1[i] >= ``'A'` `&& str1[i] <= ``'Z'``)` `                     ``|| (str1[i] >= ``'0'` `&& str1[i] <= ``'9'``)))) {` `            ``i++;` `        ``}`   `        ``// If the current character of the second string is not an` `        ``// alphanumeric character, increase the pointer j` `        ``while` `(j < len2` `               ``&& (!((str2[j] >= ``'a'` `&& str2[j] <= ``'z'``)` `                     ``|| (str2[j] >= ``'A'` `&& str2[j] <= ``'Z'``)` `                     ``|| (str2[j] >= ``'0'` `&& str2[j] <= ``'9'``)))) {` `            ``j++;` `        ``}`   `        ``// if all alphanumeric characters of both strings are same` `        ``// then return true` `        ``if` `(i == len1 && j == len2)` `            ``return` `true``;`   `        ``// if any alphanumeric characters of both strings are not same` `        ``// then return false` `        ``else` `if` `(str1[i] != str2[j])` `            ``return` `false``;`   `        ``// If current character matched,` `        ``// increase both pointers to check the next character` `        ``else` `{` `            ``i++;` `            ``j++;` `        ``}` `    ``}`   `    ``// If not same, then return false` `    ``return` `false``;` `}`   `// Function to print Equal or Unequal if strings are same or not` `void` `CompareAlphanumericUtil(string str1, string str2)` `{` `    ``bool` `res;`   `    ``// check alphanumeric equality of both strings` `    ``res = CompareAlphanumeric(str1, str2);`   `    ``// if both are alphanumeric equal, print Equal` `    ``if` `(res == ``true``)` `        ``cout << ``"Equal"` `<< endl;`   `    ``// otherwise print Unequal` `    ``else` `        ``cout << ``"Unequal"` `<< endl;` `}`   `// Driver code` `int` `main()` `{`   `    ``string str1, str2;`   `    ``str1 = ``"Ram, Shyam"``;` `    ``str2 = ``" Ram - Shyam."``;` `    ``CompareAlphanumericUtil(str1, str2);`   `    ``str1 = ``"abc123"``;` `    ``str2 = ``"123abc"``;` `    ``CompareAlphanumericUtil(str1, str2);`   `    ``return` `0;` `}`

## Java

 `// Java implementation of the approach` `import` `java.util.*;`   `class` `GFG ` `{`   `// Function to check alphanumeric` `// equality of both strings` `static` `boolean` `CompareAlphanumeric(``char``[] str1, ` `                                   ``char``[] str2) ` `{` `    ``// variable declaration` `    ``int` `i, j;` `    ``i = ``0``;` `    ``j = ``0``;`   `    ``// Length of first string` `    ``int` `len1 = str1.length;`   `    ``// Length of second string` `    ``int` `len2 = str2.length;`   `    ``// To check each and every characters` `    ``// of both string` `    ``while` `(i <= len1 && j <= len2) ` `    ``{`   `        ``// If the current character of the first string is not an` `        ``// alphanumeric character, increase the pointer i` `        ``while` `(i < len1 && (!((str1[i] >= ``'a'` `&& str1[i] <= ``'z'``) || ` `                              ``(str1[i] >= ``'A'` `&& str1[i] <= ``'Z'``) || ` `                              ``(str1[i] >= ``'0'` `&& str1[i] <= ``'9'``))))` `        ``{` `            ``i++;` `        ``}`   `        ``// If the current character of the second string is not an` `        ``// alphanumeric character, increase the pointer j` `        ``while` `(j < len2 && (!((str2[j] >= ``'a'` `&& str2[j] <= ``'z'``) || ` `                              ``(str2[j] >= ``'A'` `&& str2[j] <= ``'Z'``) || ` `                              ``(str2[j] >= ``'0'` `&& str2[j] <= ``'9'``))))` `        ``{` `            ``j++;` `        ``}`   `        ``// if all alphanumeric characters of ` `        ``// both strings are same then return true` `        ``if` `(i == len1 && j == len2)` `        ``{` `            ``return` `true``;` `        ``} ` `        `  `        ``// if any alphanumeric characters of ` `        ``// both strings are not same then return false` `        ``else` `if` `(str1[i] != str2[j]) ` `        ``{` `            ``return` `false``;` `        ``} ` `        `  `        ``// If current character matched,` `        ``// increase both pointers to ` `        ``// check the next character` `        ``else` `        ``{` `            ``i++;` `            ``j++;` `        ``}` `    ``}`   `    ``// If not same, then return false` `    ``return` `false``;` `}`   `// Function to print Equal or Unequal` `// if strings are same or not` `static` `void` `CompareAlphanumericUtil(String str1, ` `                                    ``String str2)` `{` `    ``boolean` `res;`   `    ``// check alphanumeric equality of both strings` `    ``res = CompareAlphanumeric(str1.toCharArray(), ` `                              ``str2.toCharArray());`   `    ``// if both are alphanumeric equal, ` `    ``// print Equal` `    ``if` `(res == ``true``) ` `    ``{` `        ``System.out.println(``"Equal"``);` `    ``} ` `    `  `    ``// otherwise print Unequal` `    ``else` `    ``{` `        ``System.out.println(``"Unequal"``);` `    ``}` `}`   `// Driver code` `public` `static` `void` `main(String[] args) ` `{` `    ``String str1, str2;`   `    ``str1 = ``"Ram, Shyam"``;` `    ``str2 = ``" Ram - Shyam."``;` `    ``CompareAlphanumericUtil(str1, str2);`   `    ``str1 = ``"abc123"``;` `    ``str2 = ``"123abc"``;` `    ``CompareAlphanumericUtil(str1, str2);` `}` `} `   `// This code is contributed by Rajput-Ji`

## Python3

 `# Function to check alphanumeric equality` `# of both strings` `def` `CompareAlphanumeric(str1, str2):` `    `  `    ``# variable declaration` `    ``i ``=` `0` `    ``j ``=` `0`   `    ``# Length of first string` `    ``len1 ``=` `len``(str1)`   `    ``# Length of second string` `    ``len2 ``=` `len``(str2)`   `    ``# To check each and every character of both string` `    ``while` `(i <``=` `len1 ``and` `j <``=` `len2):` `        `  `        ``# If the current character of the first string ` `        ``# is not an alphanumeric character,` `        ``# increase the pointer i` `        ``while` `(i < len1 ``and` `              ``(((str1[i] >``=` `'a'` `and` `str1[i] <``=` `'z'``) ``or` `                ``(str1[i] >``=` `'A'` `and` `str1[i] <``=` `'Z'``) ``or` `                ``(str1[i] >``=` `'0'` `and` `str1[i] <``=` `'9'``)) ``=``=` `False``)):` `            ``i ``+``=` `1`   `        ``# If the current character of the second string` `        ``# is not an alphanumeric character,` `        ``# increase the pointer j` `        ``while` `(j < len2 ``and` `              ``(((str2[j] >``=` `'a'` `and` `str2[j] <``=` `'z'``) ``or` `                ``(str2[j] >``=` `'A'` `and` `str2[j] <``=` `'Z'``) ``or` `                ``(str2[j] >``=` `'0'` `and` `str2[j] <``=` `'9'``)) ``=``=` `False``)):` `            ``j ``+``=` `1`   `        ``# if all alphanumeric characters of ` `        ``# both strings are same, then return true` `        ``if` `(i ``=``=` `len1 ``and` `j ``=``=` `len2):` `            ``return` `True`   `        ``# if any alphanumeric characters of ` `        ``# both strings are not same, then return false` `        ``elif` `(str1[i] !``=` `str2[j]):` `            ``return` `False`   `        ``# If current character matched,` `        ``# increase both pointers ` `        ``# to check the next character` `        ``else``:` `            ``i ``+``=` `1` `            ``j ``+``=` `1`   `    ``# If not same, then return false` `    ``return` `False`   `# Function to print Equal or Unequal` `# if strings are same or not` `def` `CompareAlphanumericUtil(str1, str2):` `    `  `    ``# check alphanumeric equality of both strings` `    ``res ``=` `CompareAlphanumeric(str1, str2)`   `    ``# if both are alphanumeric equal, print Equal` `    ``if` `(res ``=``=` `True``):` `        ``print``(``"Equal"``)` `        `  `    ``# otherwise print Unequal` `    ``else``:` `        ``print``(``"Unequal"``)`   `# Driver code` `if` `__name__ ``=``=` `'__main__'``:` `    ``str1 ``=` `"Ram, Shyam"` `    ``str2 ``=` `" Ram - Shyam."` `    ``CompareAlphanumericUtil(str1, str2)`   `    ``str1 ``=` `"abc123"` `    ``str2 ``=` `"123abc"` `    ``CompareAlphanumericUtil(str1, str2) `   `# This code is contributed by Surendra_Gangwar`

## C#

 `// C# implementation of the approach ` `using` `System;`   `class` `GFG` `{` `    `  `    ``// Function to check alphanumeric ` `    ``// equality of both strings ` `    ``static` `bool` `CompareAlphanumeric(``char` `[]str1, ` `                                    ``char` `[]str2) ` `    ``{ ` `        ``// variable declaration ` `        ``int` `i, j; ` `        ``i = 0; ` `        ``j = 0; ` `    `  `        ``// Length of first string ` `        ``int` `len1 = str1.Length; ` `    `  `        ``// Length of second string ` `        ``int` `len2 = str2.Length; ` `    `  `        ``// To check each and every characters ` `        ``// of both string ` `        ``while` `(i <= len1 && j <= len2) ` `        ``{ ` `    `  `            ``// If the current character of the first ` `            ``// string is not an alphanumeric character,` `            ``// increase the pointer i ` `            ``while` `(i < len1 && (!((str1[i] >= ``'a'` `&& str1[i] <= ``'z'``) || ` `                                  ``(str1[i] >= ``'A'` `&& str1[i] <= ``'Z'``) || ` `                                  ``(str1[i] >= ``'0'` `&& str1[i] <= ``'9'``)))) ` `            ``{ ` `                ``i++; ` `            ``} ` `    `  `            ``// If the current character of the second ` `            ``// string is not an alphanumeric character,` `            ``// increase the pointer j ` `            ``while` `(j < len2 && (!((str2[j] >= ``'a'` `&& str2[j] <= ``'z'``) || ` `                                  ``(str2[j] >= ``'A'` `&& str2[j] <= ``'Z'``) || ` `                                  ``(str2[j] >= ``'0'` `&& str2[j] <= ``'9'``)))) ` `            ``{ ` `                ``j++; ` `            ``} ` `    `  `            ``// if all alphanumeric characters of ` `            ``// both strings are same then return true ` `            ``if` `(i == len1 && j == len2) ` `            ``{ ` `                ``return` `true``; ` `            ``} ` `            `  `            ``// if any alphanumeric characters of ` `            ``// both strings are not same then return false ` `            ``else` `if` `(str1[i] != str2[j]) ` `            ``{ ` `                ``return` `false``; ` `            ``} ` `            `  `            ``// If current character matched, ` `            ``// increase both pointers to ` `            ``// check the next character ` `            ``else` `            ``{ ` `                ``i++; ` `                ``j++; ` `            ``} ` `        ``} ` `    `  `        ``// If not same, then return false ` `        ``return` `false``; ` `    ``} ` `    `  `    ``// Function to print Equal or Unequal ` `    ``// if strings are same or not ` `    ``static` `void` `CompareAlphanumericUtil(``string` `str1, ` `                                        ``string` `str2) ` `    ``{ ` `        ``bool` `res; ` `    `  `        ``// check alphanumeric equality of both strings ` `        ``res = CompareAlphanumeric(str1.ToCharArray(), ` `                                  ``str2.ToCharArray()); ` `    `  `        ``// if both are alphanumeric equal, ` `        ``// print Equal ` `        ``if` `(res == ``true``) ` `        ``{ ` `            ``Console.WriteLine(``"Equal"``); ` `        ``} ` `        `  `        ``// otherwise print Unequal ` `        ``else` `        ``{ ` `            ``Console.WriteLine(``"Unequal"``); ` `        ``} ` `    ``} ` `    `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``string` `str1, str2; ` `    `  `        ``str1 = ``"Ram, Shyam"``; ` `        ``str2 = ``" Ram - Shyam."``; ` `        ``CompareAlphanumericUtil(str1, str2); ` `    `  `        ``str1 = ``"abc123"``; ` `        ``str2 = ``"123abc"``; ` `        ``CompareAlphanumericUtil(str1, str2); ` `    ``} ` `}`   `// This code is contributed by AnkitRai01`

## Javascript

 ``

Output:

```Equal
Unequal```

Time Complexity: O(n*n)
Auxiliary Space: O(1), as no extra space is required

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