# Check if a string can be split into substrings starting with N followed by N characters

Given a string str, the task is to check if it can be split into substrings such that each substring starts with a numeric value followed by a number of characters represented by that numeric integer. Examples:

Input: str = “4g12y6hunter” Output: Yes Explanation: Substrings “4g12y” and “6hunter” satisfy the given condition Input: str = “31ba2a” Output: No Explanation: The entire string cannot be split into substrings of desired types

Approach:

• Check for the conditions when a split is not possible:
• If the given string does not start with a number.
• If the integer, in the beginning of a substring, is greater than the total number of succeeding characters in the remaining substring.
• If the above two condition are not satisfied, an answer is definitely possible. Hence find the substrings recursively.

Below is the implementation of the above approach:

## C++

 `// C++ Program to implement the` `// above approach` `#include ` `using` `namespace` `std;`   `// Function to check if the given` `// can be split into desired` `// substrings` `bool` `helper(string& s, ``int` `pos)` `{` `    ``// Length of the string` `    ``int` `len = s.size();`   `    ``if` `(pos >= len)` `        ``return` `true``;`   `    ``if` `(!``isdigit``(s[pos]))` `        ``return` `false``;`   `    ``int` `num = 0;`   `    ``// Traverse the string` `    ``for` `(``int` `i = pos; i < len; i++) {`   `        ``// Extract the digit` `        ``num = num * 10 + s[pos] - ``'0'``;`   `        ``// Check if the extracted number` `        ``// does not exceed the remaining` `        ``// length` `        ``if` `(i + 1 + num > len)` `            ``return` `false``;`   `        ``// Check for the remaining` `        ``// string` `        ``if` `(helper(s, i + 1 + num))` `            ``return` `true``;` `    ``}`   `    ``// If generating desired` `    ``// substrings is not possible` `    ``return` `false``;` `}`   `// Driver Code` `int` `main()` `{` `    ``string s = ``"123abc4db1c"``;` `    ``if` `(helper(s, 0))` `        ``cout << ``"Yes"``;` `    ``else` `        ``cout << ``"No"``;` `}`

## Java

 `// Java program to implement the` `// above approach` `import` `java.util.*;`   `class` `GFG{` `    `  `// Function to check if the given` `// can be split into desired` `// substrings` `public` `static` `boolean` `helper(String s, ``int` `pos)` `{` `    `  `    ``// Length of the string` `    ``int` `len = s.length();` `    `  `    ``if` `(pos >= len)` `        ``return` `true``;` `    ``if` `(!Character.isDigit(s.charAt(pos)))` `        ``return` `false``;` `    `  `    ``int` `num = ``0``;` `    `  `    ``// Traverse the string` `    ``for``(``int` `i = pos; i < len; i++)` `    ``{` `        `  `    ``// Extract the digit` `    ``num = num * ``10` `+ s.charAt(pos) - ``'0'``;` `        `  `    ``// Check if the extracted number` `    ``// does not exceed the remaining` `    ``// length` `    ``if` `(i + ``1` `+ num > len)` `        ``return` `false``;` `        `  `    ``// Check for the remaining` `    ``// string` `    ``if` `(helper(s, i + ``1` `+ num))` `        ``return` `true``;` `    ``}` `    `  `    ``// If generating desired` `    ``// substrings is not possible` `    ``return` `false``;` `}`   `// Driver code` `public` `static` `void` `main (String[] args)` `{` `    ``String s = ``"123abc4db1c"``;` `    `  `    ``if` `(helper(s, ``0``))` `        ``System.out.print(``"Yes"``);` `    ``else` `        ``System.out.print(``"No"``);` `}` `}`   `// This code is contributed by divyeshrabadiya07`

## Python3

 `# Python3 program to implement the` `# above approach`   `# Function to check if the given` `# can be split into desired` `# substrings` `def` `helper(s, pos):` `    `  `    ``# Length of the string` `    ``size ``=` `len``(s)`   `    ``if``(pos >``=` `size):` `        ``return` `True`   `    ``if``(s[pos].isdigit() ``=``=` `False``):` `        ``return` `False`   `    ``num ``=` `0`   `    ``# Traverse the string` `    ``for` `i ``in` `range``(pos, size):` `        `  `        ``# Extract the digit` `        ``num ``=` `num ``*` `10` `+` `ord``(s[pos]) ``-` `48`   `        ``# Check if the extracted number` `        ``# does not exceed the remaining` `        ``# length` `        ``if` `(i ``+` `1` `+` `num > size):` `            ``return` `False`   `        ``# Check for the remaining` `        ``# string` `        ``if` `(helper(s, i ``+` `1` `+` `num)):` `            ``return` `True`   `    ``# If generating desired` `    ``# substrings is not possible` `    ``return` `False`   `# Driver Code` `s ``=` `"123abc4db1c"``;`   `if` `(helper(s, ``0``)):` `    ``print``(``"Yes"``)` `else``:` `    ``print``(``"No"``)`   `# This code is contributed by Sanjit_Prasad`

## C#

 `// C# program to implement the` `// above approach` `using` `System;`   `class` `GFG{` `    `  `// Function to check if the given` `// can be split into desired` `// substrings` `public` `static` `bool` `helper(String s, ``int` `pos)` `{` `    `  `    ``// Length of the string` `    ``int` `len = s.Length;` `    `  `    ``if` `(pos >= len)` `        ``return` `true``;` `    ``if` `(!``char``.IsDigit(s[pos]))` `        ``return` `false``;` `    `  `    ``int` `num = 0;` `    `  `    ``// Traverse the string` `    ``for``(``int` `i = pos; i < len; i++)` `    ``{` `        `  `    ``// Extract the digit` `    ``num = num * 10 + s[pos] - ``'0'``;` `        `  `    ``// Check if the extracted number` `    ``// does not exceed the remaining` `    ``// length` `    ``if` `(i + 1 + num > len)` `        ``return` `false``;` `        `  `    ``// Check for the remaining` `    ``// string` `    ``if` `(helper(s, i + 1 + num))` `        ``return` `true``;` `    ``}` `    `  `    ``// If generating desired` `    ``// substrings is not possible` `    ``return` `false``;` `}`   `// Driver code` `public` `static` `void` `Main(String[] args)` `{` `    ``String s = ``"123abc4db1c"``;` `    `  `    ``if` `(helper(s, 0))` `        ``Console.Write(``"Yes"``);` `    ``else` `        ``Console.Write(``"No"``);` `}` `}`   `// This code is contributed by amal kumar choubey`

## Javascript

 `// JavaScript program to implement the above approach`   `// Function to check if the given` `// can be split into desired` `// substrings` `function` `helper(s, pos) {` `    ``// Length of the string` `    ``let size = s.length;` `    ``if` `(pos >= size) {` `        ``return` `true``;` `    ``}`   `    ``if` `(!/^\d+\$/.test(s[pos])) {` `        ``return` `false``;` `    ``}`   `    ``let num = 0;`   `    ``// Traverse the string` `    ``for` `(let i = pos; i < size; i++) {` `        ``// Extract the digit` `        ``num = num * 10 + parseInt(s[i]);`   `        ``// Check if the extracted number` `        ``// does not exceed the remaining` `        ``// length` `        ``if` `(i + 1 + num > size) {` `            ``return` `false``;` `        ``}`   `        ``// Check for the remaining` `        ``// string` `        ``if` `(helper(s, i + 1 + num)) {` `            ``return` `true``;` `        ``}` `    ``}`   `    ``// If generating desired` `    ``// substrings is not possible` `    ``return` `false``;` `}`   `// Driver Code` `let s = ``"123abc4db1c"``;`   `if` `(helper(s, 0)) {` `    ``console.log(``"Yes"``);` `} ``else` `{` `    ``console.log(``"No"``);` `}`   `//contributed by adityasha4x71`

Output

`Yes`

Time Complexity: O(N)
Auxiliary Space: O(1)

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