# Construct a string of length L such that each substring of length X has exactly Y distinct letters

Given the **length of the string l**, the **length of the substring x** and the number of distinct characters that a substring of length x must have are y, the task is to find a string of length l in which every substring of length x has y distinct characters.**Examples:**

Input:l = 6, x = 5, y = 3Output:abcabcExplanation:

If we take a substring of the first five characters then the substring will be “abcab”.

There are exactly three distinct characters (a, b, c) in the substring.

Similarly, if we take any substring from the string of length 5 then it will have

exactly 3 distinct characters.Input:l = 3, x = 1, y = 1Output:aaaExplanation:

If we take the substring of length 1 then it will have exactly 1 distinct character in it.

**Approach:**

To solve the problem mentioned above we follow the steps given below:

- Initialize a variable p as 97 which marks the ASCII value of lower case letter ‘a’.
- Keep incrementing the value of p till y characters.
- Then repeat the character from the first character till it’s length become equal to length of given string and return the final string.

Below is the implementation of the above approach:

## C++

`// C++ implementation to` `// construct a string of length L` `// such that each substring of length` `// X has exactly Y distinct letters.` `#include <iostream>` `using` `namespace` `std;` `void` `String(` `int` `l, ` `int` `x, ` `int` `y)` `{` ` ` `// Initialize p equal to the ASCII value of a` ` ` `int` `p = 97;` ` ` ` ` `// Iterate till the length of the string` ` ` `for` `(` `int` `j = 0; j < l ; j++)` ` ` `{` ` ` `char` `ans = (` `char` `)(p + (j % y));` ` ` `cout << ans;` ` ` `}` `}` ` ` `// Driver code` `int` `main ()` `{` ` ` `int` `l = 6;` ` ` `int` `x = 5;` ` ` `int` `y = 3;` ` ` `String(l, x, y) ;` ` ` `return` `0;` `}` `// This code is contributed by AnkitRai01` |

## Java

`// Java implementation to` `// construct a string of length L` `// such that each substring of length` `// X has exactly Y distinct letters.` `public` `class` `GFG {` ` ` ` ` `static` `void` `string(` `int` `l, ` `int` `x, ` `int` `y){` ` ` ` ` `// Initialize p equal to the ASCII value of a` ` ` `int` `p = ` `97` `;` ` ` ` ` `// Iterate till the length of the string` ` ` `for` `(` `int` `j = ` `0` `; j < l ; j++){` ` ` ` ` `char` `ans = (` `char` `)(p + (j % y));` ` ` `System.out.print(ans);` ` ` `}` ` ` ` ` `}` ` ` ` ` `// Driver code` ` ` `public` `static` `void` `main (String[] args) {` ` ` `int` `l = ` `6` `;` ` ` `int` `x = ` `5` `;` ` ` `int` `y = ` `3` `;` ` ` `string(l, x, y) ;` ` ` `}` `}` `// This code is contributed by AnkitRai01` |

## Python3

`# Python implementation to` `# construct a string of length L` `# such that each substring of length` `# X has exactly Y distinct letters.` `def` `String(l, x, y):` ` ` `# Initialize p equal to the ASCII value of a` ` ` `p ` `=` `97` ` ` `# Iterate till the length of the string` ` ` `for` `j ` `in` `range` `(l):` ` ` ` ` `ans ` `=` `chr` `(p ` `+` `j ` `%` `y)` ` ` `print` `(ans, end ` `=` `"")` ` ` `# Driver code` `l ` `=` `6` `x ` `=` `5` `y ` `=` `3` `String(l, x, y)` |

## C#

`// C# implementation to` `// construct a string of length L` `// such that each substring of length` `// X has exactly Y distinct letters.` `using` `System;` `class` `GFG {` ` ` `static` `void` `String(` `int` `l, ` `int` `x, ` `int` `y)` ` ` `{` ` ` `// Initialize p equal to the ASCII value of a` ` ` `int` `p = 97;` ` ` ` ` `// Iterate till the length of the string` ` ` `for` `(` `int` `j = 0; j < l; j++)` ` ` `{` ` ` `char` `ans = (` `char` `)(p + (j % y));` ` ` `Console.Write(ans);` ` ` `}` ` ` `}` ` ` ` ` `// Driver code` ` ` `public` `static` `void` `Main(` `string` `[] args)` ` ` `{` ` ` `int` `l = 6;` ` ` `int` `x = 5;` ` ` `int` `y = 3;` ` ` `String(l, x, y);` ` ` `}` `}` `// This code is contributed by AnkitRai01` |

## Javascript

`<script>` `// javascript implementation to` `// construct a string of length L` `// such that each substring of length` `// X has exactly Y distinct letters.` ` ` `function` `string(l , x , y){` ` ` ` ` `// Initialize p equal to the ASCII value of a` ` ` `var` `p = 97;` ` ` `// Iterate till the length of the string` ` ` `for` `(` `var` `j = 0; j < l ; j++){` ` ` ` ` `var` `ans = String.fromCharCode(p + (j % y));` ` ` `document.write(ans);` ` ` `}` ` ` `}` `// Driver code` `var` `l = 6;` `var` `x = 5;` `var` `y = 3;` `string(l, x, y) ;` `// This code contributed by shikhasingrajput` `</script>` |

**Output:**

abcabc

Time Complexity: O(l)

Auxiliary Space: O(1)