# Queries for rotation and Kth character of the given string in constant time

Given a string str, the task is to perform the following type of queries on the given string:

1. (1, K): Left rotate the string by K characters.
2. (2, K): Print the Kth character of the string.

Examples:

Input: str = “abcdefgh”, q[][] = {{1, 2}, {2, 2}, {1, 4}, {2, 7}}
Output:
d
e
Query 1: str = “cdefghab”
Query 2: 2nd character is d
Query 3: str = “ghabcdef”
Query 4: 7th character is e

Input: str = “abc”, q[][] = {{1, 2}, {2, 2}}
Output:
a

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: The main observation here is that the string doesn’t need to be rotated in every query instead we can create a pointer ptr pointing to the first character of the string and which can be updated for every rotation as ptr = (ptr + K) % N where K the integer by which the string needs to be rotated and N is the length of the string. Now for every query of the second type, the Kth character can be found by str[(ptr + K – 1) % N].

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `#define size 2 ` ` `  `// Function to perform the required ` `// queries on the given string ` `void` `performQueries(string str, ``int` `n, ` `                    ``int` `queries[][size], ``int` `q) ` `{ ` ` `  `    ``// Pointer pointing to the current starting ` `    ``// character of the string ` `    ``int` `ptr = 0; ` ` `  `    ``// For every query ` `    ``for` `(``int` `i = 0; i < q; i++) { ` ` `  `        ``// If the query is to rotate the string ` `        ``if` `(queries[i] == 1) { ` ` `  `            ``// Update the pointer pointing to the ` `            ``// starting character of the string ` `            ``ptr = (ptr + queries[i]) % n; ` `        ``} ` `        ``else` `{ ` ` `  `            ``int` `k = queries[i]; ` ` `  `            ``// Index of the kth character in the ` `            ``// current rotation of the string ` `            ``int` `index = (ptr + k - 1) % n; ` ` `  `            ``// Print the kth character ` `            ``cout << str[index] << ``"\n"``; ` `        ``} ` `    ``} ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``string str = ``"abcdefgh"``; ` `    ``int` `n = str.length(); ` ` `  `    ``int` `queries[][size] = { { 1, 2 }, { 2, 2 },  ` `                            ``{ 1, 4 }, { 2, 7 } }; ` `    ``int` `q = ``sizeof``(queries) / ``sizeof``(queries); ` ` `  `    ``performQueries(str, n, queries, q); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java implementation of the above approach ` `import` `java.util.*; ` `class` `GFG  ` `{ ` `static` `int` `size = ``2``; ` ` `  `// Function to perform the required ` `// queries on the given string ` `static` `void` `performQueries(String str, ``int` `n, ` `                           ``int` `queries[][], ``int` `q) ` `{ ` ` `  `    ``// Pointer pointing to the current  ` `    ``// starting character of the string ` `    ``int` `ptr = ``0``; ` ` `  `    ``// For every query ` `    ``for` `(``int` `i = ``0``; i < q; i++)  ` `    ``{ ` ` `  `        ``// If the query is to rotate the string ` `        ``if` `(queries[i][``0``] == ``1``) ` `        ``{ ` ` `  `            ``// Update the pointer pointing to the ` `            ``// starting character of the string ` `            ``ptr = (ptr + queries[i][``1``]) % n; ` `        ``} ` `        ``else`  `        ``{ ` `            ``int` `k = queries[i][``1``]; ` ` `  `            ``// Index of the kth character in the ` `            ``// current rotation of the string ` `            ``int` `index = (ptr + k - ``1``) % n; ` ` `  `            ``// Print the kth character ` `            ``System.out.println(str.charAt(index)); ` `        ``} ` `    ``} ` `} ` ` `  `// Driver code ` `public` `static` `void` `main(String[] args) ` `{ ` `    ``String str = ``"abcdefgh"``; ` `    ``int` `n = str.length(); ` ` `  `    ``int` `queries[][] = { { ``1``, ``2` `}, { ``2``, ``2` `},  ` `                        ``{ ``1``, ``4` `}, { ``2``, ``7` `} }; ` `    ``int` `q = queries.length; ` ` `  `    ``performQueries(str, n, queries, q); ` `} ` `}  ` ` `  `// This code is contributed by 29AjayKumar `

## Python3

 `# Python3 implementation of the approach  ` `size ``=` `2` ` `  `# Function to perform the required  ` `# queries on the given string  ` `def` `performQueries(string, n, queries, q) :  ` ` `  `    ``# Pointer pointing to the current starting  ` `    ``# character of the string  ` `    ``ptr ``=` `0``;  ` ` `  `    ``# For every query  ` `    ``for` `i ``in` `range``(q) : ` ` `  `        ``# If the query is to rotate the string  ` `        ``if` `(queries[i][``0``] ``=``=` `1``) :  ` ` `  `            ``# Update the pointer pointing to the  ` `            ``# starting character of the string  ` `            ``ptr ``=` `(ptr ``+` `queries[i][``1``]) ``%` `n;  ` `             `  `        ``else` `: ` ` `  `            ``k ``=` `queries[i][``1``];  ` ` `  `            ``# Index of the kth character in the  ` `            ``# current rotation of the string  ` `            ``index ``=` `(ptr ``+` `k ``-` `1``) ``%` `n;  ` ` `  `            ``# Print the kth character  ` `            ``print``(string[index]);  ` ` `  `# Driver code  ` `if` `__name__ ``=``=` `"__main__"` `:  ` ` `  `    ``string ``=` `"abcdefgh"``;  ` `    ``n ``=` `len``(string);  ` ` `  `    ``queries ``=` `[[ ``1``, ``2` `], [ ``2``, ``2` `],  ` `               ``[ ``1``, ``4` `], [ ``2``, ``7` `]];  ` `    ``q ``=` `len``(queries);  ` ` `  `    ``performQueries(string, n, queries, q);  ` `     `  `# This code is contributed by AnkitRai01 `

## C#

 `// C# implementation of the approach ` `using` `System; ` `     `  `class` `GFG  ` `{ ` `static` `int` `size = 2; ` ` `  `// Function to perform the required ` `// queries on the given string ` `static` `void` `performQueries(String str, ``int` `n, ` `                           ``int` `[,]queries, ``int` `q) ` `{ ` ` `  `    ``// Pointer pointing to the current  ` `    ``// starting character of the string ` `    ``int` `ptr = 0; ` ` `  `    ``// For every query ` `    ``for` `(``int` `i = 0; i < q; i++)  ` `    ``{ ` ` `  `        ``// If the query is to rotate the string ` `        ``if` `(queries[i, 0] == 1) ` `        ``{ ` ` `  `            ``// Update the pointer pointing to the ` `            ``// starting character of the string ` `            ``ptr = (ptr + queries[i, 1]) % n; ` `        ``} ` `        ``else` `        ``{ ` `            ``int` `k = queries[i, 1]; ` ` `  `            ``// Index of the kth character in the ` `            ``// current rotation of the string ` `            ``int` `index = (ptr + k - 1) % n; ` ` `  `            ``// Print the kth character ` `            ``Console.WriteLine(str[index]); ` `        ``} ` `    ``} ` `} ` ` `  `// Driver code ` `public` `static` `void` `Main(String[] args) ` `{ ` `    ``String str = ``"abcdefgh"``; ` `    ``int` `n = str.Length; ` ` `  `    ``int` `[,]queries = { { 1, 2 }, { 2, 2 },  ` `                       ``{ 1, 4 }, { 2, 7 } }; ` `    ``int` `q = queries.GetLength(0); ` ` `  `    ``performQueries(str, n, queries, q); ` `} ` `} ` ` `  `// This code is contributed by PrinciRaj1992 `

Output:

```d
e
```

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