Given a string **str**. The task is to find all possible number of strings that can be obtained by replacing the “$” with alphabets in the given string.**Note**: Alphabets should be placed in such a way that the string is always alternating in vowels and consonants, and the string must always start with a consonant. It is assumed that such a string is always possible, i.e. there is no need to care about the characters other than “$”.**Examples**:

Input: str = "y$s"Output: 5 $ can be replaced with any of the 5 vowels. So, there can be 5 strings.Input: str = "s$$e$"Output: 2205

**Approach:** It is given that the string will start with a consonant. So, if ‘$’ is at even position(considering 0-based indexing) then there should be a consonant else there should be a vowel. Also, given that there is no need to care about the characters other than “$”, i.e., characters other than “$” are placed correctly in the string maintaining the alternating consonant and vowel sequence. Let us understand the problem with an example.

str = “s$$e$”

Here we have to find the number of ways to form a string with given constraints.

- First occurrence of $ is at 2nd position i.e. 1st index, so we can use 5 vowels.
- Second occurrence of $ is at 3rd position, so we can use 21 consonants.
- Third occurrence of $ is at 5th position, so we can use 21 consonants.
So, total number of ways to form above string is

= 5*21*21 = 2205

Below is the implementation of the above approach:

## C++

`// C++ implementation of above approach` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Function to find the count of strings` `int` `countStrings(string s)` `{` ` ` `// Variable to store the final result` ` ` `long` `sum = 1;` ` ` `// Loop iterating through string` ` ` `for` `(` `int` `i = 0; i < s.size(); i++) {` ` ` `// If '$' is present at the even` ` ` `// position in the string` ` ` `if` `(i % 2 == 0 && s[i] == ` `'$'` `)` ` ` `//'sum' is multiplied by 21` ` ` `sum *= 21;` ` ` `// If '$' is present at the odd` ` ` `// position in the string` ` ` `else` `if` `(s[i] == ` `'$'` `)` ` ` `//'sum' is multiplied by 5` ` ` `sum *= 5;` ` ` `}` ` ` `return` `sum;` `}` `// Driver code` `int` `main()` `{` ` ` `// Let the string 'str' be s$$e$` ` ` `string str = ` `"s$$e$"` `;` ` ` `// Print result` ` ` `cout << countStrings(str) << endl;` ` ` `return` `0;` `}` |

## Java

`// Java implementation of above approach` `import` `java.util.*;` `import` `java.lang.*;` `import` `java.io.*;` `class` `GFG{` `// Function to find the count of strings` `static` `int` `countStrings(String s)` `{` ` ` `// Variable to store the final result` ` ` `int` `sum = ` `1` `;` ` ` ` ` `// Loop iterating through string` ` ` `for` `(` `int` `i = ` `0` `; i < s.length(); i++) {` ` ` ` ` `// If '$' is present at the even` ` ` `// position in the string` ` ` `if` `(i % ` `2` `== ` `0` `&& s.charAt(i) == ` `'$'` `)` ` ` ` ` `//'sum' is multiplied by 21` ` ` `sum *= ` `21` `;` ` ` ` ` `// If '$' is present at the odd` ` ` `// position in the string` ` ` `else` `if` `(s.charAt(i) == ` `'$'` `)` ` ` ` ` `//'sum' is multiplied by 5` ` ` `sum *= ` `5` `;` ` ` `}` ` ` ` ` `return` `sum;` `}` ` ` `// Driver code` `public` `static` `void` `main(String args[])` `{` ` ` `// Let the string 'str' be s$$e$` ` ` `String str = ` `"s$$e$"` `;` ` ` ` ` `// Print result` ` ` `System.out.println(countStrings(str));` `}` `}` |

## Python 3

`# Python 3 implementation of above approach` `# Function to find the count of strings` `def` `countStrings(s):` ` ` ` ` `# Variable to store the final result` ` ` `sum` `=` `1` ` ` `# Loop iterating through string` ` ` `for` `i ` `in` `range` `(` `len` `(s)):` ` ` `# If '$' is present at the even` ` ` `# position in the string` ` ` `if` `(i ` `%` `2` `=` `=` `0` `and` `s[i] ` `=` `=` `'$'` `):` ` ` `#'sum' is multiplied by 21` ` ` `sum` `*` `=` `21` ` ` `# If '$' is present at the odd` ` ` `# position in the string` ` ` `elif` `(s[i] ` `=` `=` `'$'` `):` ` ` `# 'sum' is multiplied by 5` ` ` `sum` `*` `=` `5` ` ` `return` `sum` `# Driver code` `if` `__name__ ` `=` `=` `"__main__"` `:` ` ` ` ` `# Let the string 'str' be s$$e$` ` ` `str` `=` `"s$$e$"` ` ` `# Print result` ` ` `print` `(countStrings(` `str` `))` ` ` `# this code is contributed by ChitraNayal` |

## C#

`// C# implementation of above approach` `using` `System;` `class` `GFG{` ` ` `// Function to find the count of strings` `static` `int` `countStrings(String s)` `{` ` ` `// Variable to store the final result` ` ` `int` `sum = 1;` ` ` ` ` `// Loop iterating through string` ` ` `for` `(` `int` `i = 0; i < s.Length; i++) {` ` ` ` ` `// If '$' is present at the even` ` ` `// position in the string` ` ` `if` `(i % 2 == 0 && s[i] == ` `'$'` `)` ` ` ` ` `//'sum' is multiplied by 21` ` ` `sum *= 21;` ` ` ` ` `// If '$' is present at the odd` ` ` `// position in the string` ` ` `else` `if` `(s[i] == ` `'$'` `)` ` ` ` ` `//'sum' is multiplied by 5` ` ` `sum *= 5;` ` ` `}` ` ` ` ` `return` `sum;` `}` ` ` `// Driver code` `public` `static` `void` `Main()` `{` ` ` `// Let the string 'str' be s$$e$` ` ` `String str = ` `"s$$e$"` `;` ` ` ` ` `// Print result` ` ` `Console.WriteLine(countStrings(str));` `}` `}` |

## PHP

`<?php` `// PHP implementation of above approach` `// Function to find the count of strings` `function` `countStrings(` `$s` `)` `{` ` ` `// Variable to store the` ` ` `// final result` ` ` `$sum` `= 1;` ` ` `// Loop iterating through string` ` ` `for` `(` `$i` `= 0; ` `$i` `< ` `strlen` `(` `$s` `); ` `$i` `++)` ` ` `{` ` ` `// If '$' is present at the even` ` ` `// position in the string` ` ` `if` `(` `$i` `% 2 == 0 && ` `$s` `[` `$i` `] == ` `'$'` `)` ` ` `//'sum' is multiplied by 21` ` ` `$sum` `*= 21;` ` ` `// If '$' is present at the odd` ` ` `// position in the string` ` ` `else` `if` `(` `$s` `[` `$i` `] == ` `'$'` `)` ` ` `//'sum' is multiplied by 5` ` ` `$sum` `*= 5;` ` ` `}` ` ` `return` `$sum` `;` `}` `// Driver code` `// Let the string 'str' be s$$e$` `$str` `= ` `"s\$\$e\$"` `;` `// Print result` `echo` `countStrings(` `$str` `);` `// This code is contributed by Ryuga` `?>` |

## Javascript

`<script>` `// javascript implementation of above approach` `// Function to find the count of strings` `function` `countStrings( s)` `{` ` ` `// Variable to store the final result` ` ` `let sum = 1;` ` ` `// Loop iterating through string` ` ` `for` `(let i = 0; i < s.length; i++)` ` ` `{` ` ` `// If '$' is present at the even` ` ` `// position in the string` ` ` `if` `(i % 2 == 0 && s[i] == ` `'$'` `)` ` ` `//'sum' is multiplied by 21` ` ` `sum *= 21;` ` ` `// If '$' is present at the odd` ` ` `// position in the string` ` ` `else` `if` `(s[i] == ` `'$'` `)` ` ` `//'sum' is multiplied by 5` ` ` `sum *= 5;` ` ` `}` ` ` `return` `sum;` `}` `// Driver code` ` ` `// Let the string 'str' be s$$e$` ` ` `let str = ` `"s$$e$"` `;` ` ` `// Print result` ` ` `document.write(countStrings(str));` ` ` `// This code is contributed by gauravrajput1` `</script>` |

**Output:**

2205