在旋转字符串中插入字符

给定一个大小为N的字符数组arr[]和一个整数K 。您必须将字符一个一个地插入到一个空字符串中，以便每次插入都在前一个插入右侧的K个位置之后完成，并且字符串是循环的。任务是找到最后一次插入完成后的字符

例子：

Input: arr[] = {‘1’, ‘2’, ‘3’, ‘4’, ‘5’}, K = 2 
Output: 1 
After the first insertion string becomes “1” 
After the second insertion string becomes “12” 
After third insertion, as the previous insertion was at position 2. 
So, the current insertion has to be at 2 + 2 i.e. 4th position. 
Since, the string is circular so moving 2 positions to the right will 
be “1|2” -> “12|” and the final string will be “123” 
After the fourth insertion, “123” -> “1|23” -> “12|3” i.e. “1243” 
After the fifth insertion, “1243” -> “1243|” -> “1|243” i.e. “15243” 
The last character inserted after the character ‘1’ 

Input: arr[] = {‘1’, ‘2’, ‘3’, ‘4’, ‘5’}, K = 1 
Output: 1 
Final string is “15324” 

方法：对于每个字符，将其插入所需的位置，并跟踪前一个位置和完成前一个插入的字符。插入所有字符后，打印最后一次插入完成后的字符。

下面是上述方法的实现：

C++

// C++ implementation of the approach
#include 
using namespace std;
 
// Function to insert the character
char Insert(char arr[], int n, int k)
{
    // To store last position where
    // the insertion is done
    int ind = 0;
 
    // To store size of the string
    int sz = 0;
 
    // To store the modified string
    string s = "";
 
    // To store characters
    char ch = arr[0];
 
    // Add first character to the string
    s += ch;
 
    // Update the size
    sz = 1;
 
    // Update the index of last insertion
    ind = 0;
 
    // Insert all other characters to the string
    for (int i = 1; i < n; i++) {
 
        // Take the character
        ch = arr[i];
 
        // Take substring upto ind
        string s1 = s.substr(0, ind + 1);
 
        // Take modulo value of k with
        // the size of the string
        int temp = k % sz;
 
        // Check if we need to move to
        // the start of the string
        int ro = temp - min(temp, sz - ind - 1);
 
        // If we don't need to move to start of the string
        if (ro == 0) {
 
            // Take substring from upto temp
            string s2 = s.substr(ind + 1, temp);
 
            // Take substring which will be after
            // the inserted character
            string s3 = s.substr(ind + temp + 1,
                                 sz - ind - temp - 1);
 
            // Insert into the string
            s = s1 + s2 + ch + s3;
 
            // Store new inserted position
            ind = s1.size() + s2.size();
 
            // Store size of the new string
            // Technically sz + 1
            sz = s.size();
        }
 
        // If we need to move to start of the string
        else {
 
            // Take substring which will before
            // the inserted character
            string s2 = s.substr(0, ro);
 
            // Take substring which will be after
            // the inserted character
            string s3 = s.substr(ro, sz - ro);
 
            // Insert into the string
            s = s2 + ch + s3;
 
            // Store new inserted position
            ind = s2.size();
 
            // Store size of the new string
            // Technically sz + 1
            sz = s.size();
        }
    }
 
    // Return the required character
    if (ind == 0)
        return s[sz - 1];
    else
        return s[ind - 1];
}
 
// Driver code
int main()
{
    char arr[] = { '1', '2', '3', '4', '5' };
 
    int k = 2;
 
    int n = sizeof(arr) / sizeof(arr[0]);
 
    // Function call
    cout << Insert(arr, n, k);
 
    return 0;
}

Java

// Java implementation of the approach
import java.util.*;
 
class GFG{
     
// Function to insert the character
public static char Insert(char arr[], int n, int k)
{
     
    // To store last position where
    // the insertion is done
    int ind = 0;
     
    // To store size of the string
    int sz = 0;
     
    // To store the modified string
    String s = "";
     
    // To store characters
    char ch = arr[0];
     
    // Add first character to the string
    s += ch;
     
    // Update the size
    sz = 1;
     
    // Update the index of last insertion
    ind = 0;
     
    // Insert all other characters to the string
    for(int i = 1; i < n; i++)
    {
         
        // Take the character
        ch = arr[i];
         
        // Take substring upto ind
        String s1 = s.substring(0, ind + 1);
         
        // Take modulo value of k with
        // the size of the string
        int temp = k % sz;
         
        // Check if we need to move to
        // the start of the string
        int ro = temp - Math.min(temp, sz - ind - 1);
         
        // If we don't need to move to
        // start of the string
        if (ro == 0)
        {
             
            // Take substring from upto temp
            String s2 = s.substring(ind + 1,
                                    ind + 1 + temp);
                                     
            // Take substring which will be after
            // the inserted character
            String s3 = s.substring(ind + temp + 1, sz);
             
            // Insert into the string
            s = s1 + s2 + ch + s3;
             
            // Store new inserted position
            ind = s1.length() + s2.length();
             
            // Store size of the new string
            // Technically sz + 1
            sz = s.length();
        }
         
        // If we need to move to start of the string
        else
        {
             
            // Take substring which will before
            // the inserted character
            String s2 = s.substring(0, ro);
             
            // Take substring which will be after
            // the inserted character
            String s3 = s.substring(ro, sz);
             
            // Insert into the string
            s = s2 + ch + s3;
             
            // Store new inserted position
            ind = s2.length();
             
            // Store size of the new string
            // Technically sz + 1
            sz = s.length();
        }
    }
     
    // Return the required character
    if (ind == 0)
    {
        return s.charAt(sz - 1);
    }
    else
    {
        return s.charAt(ind - 1);
    }
}
 
// Driver code
public static void main(String []args)
{
    char arr[] = { '1', '2', '3', '4', '5' };
    int k = 2;
    int n = arr.length;
     
    // Function call
    System.out.println(Insert(arr, n, k));
}
}
 
// This code is contributed by avanitrachhadiya2155

Python3

# Python3 implementation of the approach
 
# Function to insert the character
def insert(arr: list, n: int, k: int) -> chr:
 
    # To store last position where
    # the insertion is done
    ind = 0
 
    # To store size of the string
    sz = 0
 
    # To store the modified string
    s = ""
 
    # To store characters
    ch = arr[0]
 
    # Add first character to the string
    s += ch
 
    # Update the size
    sz = 1
 
    # Update the index of last insertion
    ind = 0
 
    # Insert all other characters to the string
    for i in range(1, n):
 
        # Take the character
        ch = arr[i]
 
        # Take substring upto ind
        s1 = s[0:ind + 1]
 
        # Take modulo value of k with
        # the size of the string
        temp = k % sz
 
        # Check if we need to move to
        # the start of the string
        ro = temp - min(temp, sz - ind - 1)
 
        # If we don't need to move to start of the string
        if ro == 0:
 
            # Take substring from upto temp
            s2 = s[ind + 1:ind + 1 + temp]
 
            # Take substring which will be after
            # the inserted character
            s3 = s[ind + temp + 1:sz]
 
            # Insert into the string
            s = s1 + s2 + ch + s3
 
            # Store new inserted position
            ind = len(s1) + len(s2)
 
            # Store size of the new string
            # Technically sz + 1
            sz = len(s)
 
        # If we need to move to start of the string
        else:
 
            # Take substring which will before
            # the inserted character
            s2 = s[:ro]
 
            # Take substring which will be after
            # the inserted character
            s3 = s[ro:sz]
 
            # Insert into the string
            s = s2 + ch + s3
 
            # Store new inserted position
            ind = len(s2)
 
            # Store size of the new string
            # Technically sz + 1
            sz = len(s)
 
    # Return the required character
    if ind == 0:
        return s[sz - 1]
    else:
        return s[ind - 1]
 
# Driver Code
if __name__ == "__main__":
    arr = ['1', '2', '3', '4', '5']
    k = 2
    n = len(arr)
 
    # Function call
    print(insert(arr, n, k))
 
# This code is contributed by
# sanjeev2552

C#

// C# implementation of the approach
using System;
 
class GFG{
     
// Function to insert the character
static char Insert(char[] arr, int n, int k)
{
     
    // To store last position where
    // the insertion is done
    int ind = 0;
  
    // To store size of the string
    int sz = 0;
  
    // To store the modified string
    String s = "";
     
    // To store characters
    char ch = arr[0];
     
    // Add first character to the string
    s += ch;
  
    // Update the size
    sz = 1;
  
    // Update the index of last insertion
    ind = 0;
  
    // Insert all other characters to the string
    for(int i = 1; i < n; i++)
    {
         
        // Take the character
        ch = arr[i];
         
        // Take substring upto ind
        string s1 = s.Substring(0, ind + 1);
         
        // Take modulo value of k with
        // the size of the string
        int temp = k % sz;
         
        // Check if we need to move to
        // the start of the string
        int ro = temp - Math.Min(temp, sz - ind - 1);
         
        // If we don't need to move to
        // start of the string
        if (ro == 0)
        {
             
            // Take substring from upto temp
            string s2 = s.Substring(ind + 1, temp);
             
            // Take substring which will be after
            // the inserted character
            string s3 = s.Substring(ind + temp + 1,
                               sz - ind - temp - 1);
                                
            // Insert into the string
            s = s1 + s2 + ch + s3;
             
            // Store new inserted position
            ind = s1.Length + s2.Length;
             
            // Store size of the new string
            // Technically sz + 1
            sz = s.Length;
        }
         
        // If we need to move to start of the string
        else
        {
             
            // Take substring which will before
            // the inserted character
            string s2 = s.Substring(0, ro);
             
            // Take substring which will be after
            // the inserted character
            string s3 = s.Substring(ro, sz - ro);
             
            // Insert into the string
            s = s2 + ch + s3;
             
            // Store new inserted position
            ind = s2.Length;
             
            // Store size of the new string
            // Technically sz + 1
            sz = s.Length;
        }
    }
     
    // Return the required character
    if (ind == 0)
    {
        return s[sz - 1];
    }
    else
    {
        return s[ind - 1];
    }
}
 
// Driver code
static public void Main()
{
    char[] arr = { '1', '2', '3', '4', '5' };
    int k = 2;
    int n = arr.Length;
     
    // Function call
    Console.WriteLine(Insert(arr, n, k));
}
}
 
// This code is contributed by rag2127

Javascript

// Javascript implementation of the approach
 
// Function to insert the character
function Insert(arr,n,k)
{
    // To store last position where
    // the insertion is done
    let ind = 0;
      
    // To store size of the string
    let sz = 0;
      
    // To store the modified string
    let s = "";
      
    // To store characters
    let ch = arr[0];
      
    // Add first character to the string
    s += ch;
      
    // Update the size
    sz = 1;
      
    // Update the index of last insertion
    ind = 0;
      
    // Insert all other characters to the string
    for(let i = 1; i < n; i++)
    {
          
        // Take the character
        ch = arr[i];
          
        // Take substring upto ind
        let s1 = s.substring(0, ind + 1);
          
        // Take modulo value of k with
        // the size of the string
        let temp = k % sz;
          
        // Check if we need to move to
        // the start of the string
        let ro = temp - Math.min(temp, sz - ind - 1);
          
        // If we don't need to move to
        // start of the string
        if (ro == 0)
        {
              
            // Take substring from upto temp
            let s2 = s.substring(ind + 1,
                                    ind + 1 + temp);
                                      
            // Take substring which will be after
            // the inserted character
            let s3 = s.substring(ind + temp + 1, sz);
              
            // Insert into the string
            s = s1 + s2 + ch + s3;
              
            // Store new inserted position
            ind = s1.length + s2.length;
              
            // Store size of the new string
            // Technically sz + 1
            sz = s.length;
        }
          
        // If we need to move to start of the string
        else
        {
              
            // Take substring which will before
            // the inserted character
            let s2 = s.substring(0, ro);
              
            // Take substring which will be after
            // the inserted character
            let s3 = s.substring(ro, sz);
              
            // Insert into the string
            s = s2 + ch + s3;
              
            // Store new inserted position
            ind = s2.length;
              
            // Store size of the new string
            // Technically sz + 1
            sz = s.length;
        }
    }
      
    // Return the required character
    if (ind == 0)
    {
        return s[sz - 1];
    }
    else
    {
        return s[ind - 1];
    }
}
 
// Driver code
let arr=['1', '2', '3', '4', '5' ];
let  k = 2;
let n = arr.length;
 
document.write(Insert(arr, n, k));
 
 
// This code is contributed by ab2127

输出：

1