阵列旋转的逆向算法

本文概述

• C ++
• C
• Java
• python
• C#
• 的PHP

编写一个函数rotate(arr [], d, n), 该函数将大小为n的arr []旋转d个元素。

范例：

Input :  arr[] = [1, 2, 3, 4, 5, 6, 7]
         d = 2
Output : arr[] = [3, 4, 5, 6, 7, 1, 2]

将上面的数组旋转2将使数组

推荐：请在"

实践

首先, 在继续解决方案之前。

在d中讨论了通过d个元素旋转数组的前3种方法。

这个

发布。

方法4(逆向算法)：

算法：

rotate(arr[], d, n)
  reverse(arr[], 1, d) ;
  reverse(arr[], d + 1, n);
  reverse(arr[], 1, n);

令AB为输入数组的两个部分, 其中A = arr [0..d-1]和B = arr [d..n-1]。该算法的思想是：

• 反转A以获得ArB, 其中Ar反转A。
• 反转B以获得ArBr, 其中Br是B的反转。
• 取反得到(ArBr)r = BA。

范例：

令数组为arr [] = [1、2、3、4、5、6、7], d = 2和n = 7

A = [1, 2]和B = [3, 4, 5, 6, 7]

• 反向A, 我们得到ArB = [2、1、3、4、5、6、7]
• 反向B, 我们得到ArBr = [2, 1, 7, 6, 6, 5, 4, 3]
• 颠倒全部, 我们得到(ArBr)r = [3, 4, 5, 5, 6, 7, 1, 2]

下面是上述方法的实现：

C ++

// C++ program for reversal algorithm
// of array rotation
#include <bits/stdc++.h>
using namespace std;
 
/*Function to reverse arr[] from index start to end*/
void reverseArray( int arr[], int start, int end)
{
     while (start < end) {
         int temp = arr[start];
         arr[start] = arr[end];
         arr[end] = temp;
         start++;
         end--;
     }
}
 
/* Function to left rotate arr[] of size n by d */
void leftRotate( int arr[], int d, int n)
{
     if (d == 0)
         return ;
     // in case the rotating factor is
     // greater than array length
     d = d % n;
 
     reverseArray(arr, 0, d - 1);
     reverseArray(arr, d, n - 1);
     reverseArray(arr, 0, n - 1);
}
 
// Function to print an array
void printArray( int arr[], int size)
{
     for ( int i = 0; i < size; i++)
         cout << arr[i] << " " ;
}
 
/* Driver program to test above functions */
int main()
{
     int arr[] = { 1, 2, 3, 4, 5, 6, 7 };
     int n = sizeof (arr) / sizeof (arr[0]);
     int d = 2;
 
     // Function calling
     leftRotate(arr, d, n);
     printArray(arr, n);
 
     return 0;
}

C

// C/C++ program for reversal algorithm of array rotation
#include <stdio.h>
 
/*Utility function to print an array */
void printArray( int arr[], int size);
 
/* Utility function to reverse arr[] from start to end */
void reverseArray( int arr[], int start, int end);
 
/* Function to left rotate arr[] of size n by d */
void leftRotate( int arr[], int d, int n)
{
 
     if (d == 0)
         return ;
     // in case the rotating factor is
     // greater than array length
     d = d % n;
 
     reverseArray(arr, 0, d - 1);
     reverseArray(arr, d, n - 1);
     reverseArray(arr, 0, n - 1);
}
 
/*UTILITY FUNCTIONS*/
/* function to print an array */
void printArray( int arr[], int size)
{
     int i;
     for (i = 0; i < size; i++)
         printf ( "%d " , arr[i]);
}
 
/*Function to reverse arr[] from index start to end*/
void reverseArray( int arr[], int start, int end)
{
     int temp;
     while (start < end) {
         temp = arr[start];
         arr[start] = arr[end];
         arr[end] = temp;
         start++;
         end--;
     }
}
 
/* Driver program to test above functions */
int main()
{
     int arr[] = { 1, 2, 3, 4, 5, 6, 7 };
     int n = sizeof (arr) / sizeof (arr[0]);
     int d = 2;
 
     leftRotate(arr, d, n);
     printArray(arr, n);
     return 0;
}

Java

// Java program for reversal algorithm of array rotation
import java.io.*;
 
class LeftRotate {
     /* Function to left rotate arr[] of size n by d */
     static void leftRotate( int arr[], int d)
     {
 
         if (d == 0 )
             return ;
 
         int n = arr.length;
         // in case the rotating factor is
         // greater than array length
         d = d % n;
         reverseArray(arr, 0 , d - 1 );
         reverseArray(arr, d, n - 1 );
         reverseArray(arr, 0 , n - 1 );
     }
 
     /*Function to reverse arr[] from index start to end*/
     static void reverseArray( int arr[], int start, int end)
     {
         int temp;
         while (start < end) {
             temp = arr[start];
             arr[start] = arr[end];
             arr[end] = temp;
             start++;
             end--;
         }
     }
 
     /*UTILITY FUNCTIONS*/
     /* function to print an array */
     static void printArray( int arr[])
     {
         for ( int i = 0 ; i < arr.length; i++)
             System.out.print(arr[i] + " " );
     }
 
     /* Driver program to test above functions */
     public static void main(String[] args)
     {
         int arr[] = { 1 , 2 , 3 , 4 , 5 , 6 , 7 };
         int n = arr.length;
         int d = 2 ;
 
         leftRotate(arr, d); // Rotate array by d
         printArray(arr);
     }
}
/*This code is contributed by Devesh Agrawal*/

python

# Python program for reversal algorithm of array rotation
 
# Function to reverse arr[] from index start to end
 
 
def reverseArray(arr, start, end):
     while (start < end):
         temp = arr[start]
         arr[start] = arr[end]
         arr[end] = temp
         start + = 1
         end = end - 1
 
# Function to left rotate arr[] of size n by d
 
 
def leftRotate(arr, d):
 
     if d = = 0 :
         return
     n = len (arr)
     # in case the rotating factor is
     # greater than array length
     d = d % n
     reverseArray(arr, 0 , d - 1 )
     reverseArray(arr, d, n - 1 )
     reverseArray(arr, 0 , n - 1 )
 
# Function to print an array
 
 
def printArray(arr):
     for i in range ( 0 , len (arr)):
         print arr[i], # Driver function to test above functions
arr = [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]
n = len (arr)
d = 2
 
leftRotate(arr, d)  # Rotate array by 2
printArray(arr)
 
# This code is contributed by Devesh Agrawal

C#

// C# program for reversal algorithm
// of array rotation
using System;
 
class GFG {
     /* Function to left rotate arr[]
     of size n by d */
     static void leftRotate( int [] arr, int d)
     {
 
         if (d == 0)
             return ;
         int n = arr.Length;
           // in case the rotating factor is
         // greater than array length
         d = d % n;
         reverseArray(arr, 0, d - 1);
         reverseArray(arr, d, n - 1);
         reverseArray(arr, 0, n - 1);
     }
 
     /* Function to reverse arr[] from
     index start to end*/
     static void reverseArray( int [] arr, int start, int end)
     {
         int temp;
         while (start < end) {
             temp = arr[start];
             arr[start] = arr[end];
             arr[end] = temp;
             start++;
             end--;
         }
     }
 
     /*UTILITY FUNCTIONS*/
     /* function to print an array */
     static void printArray( int [] arr)
     {
         for ( int i = 0; i < arr.Length; i++)
             Console.Write(arr[i] + " " );
     }
 
     // Driver code
     public static void Main()
     {
         int [] arr = { 1, 2, 3, 4, 5, 6, 7 };
         int n = arr.Length;
         int d = 2;
 
         leftRotate(arr, d); // Rotate array by 2
         printArray(arr);
     }
}
 
// This code is contributed by Sam007

的PHP

<?php
// PHP program for reversal
// algorithm of array rotation
 
/* Function to left rotate
    arr of size n by d */
function leftRotate(& $arr , $d , $n )
{
 
     if ( $d == 0)
         return ;
       // in case the rotating factor is
       // greater than array length
       $d = ( $d % $n );
     reverseArray( $arr , 0, $d - 1);
     reverseArray( $arr , $d , $n - 1);
     reverseArray( $arr , 0, $n - 1);
}
 
/*Function to reverse $arr
   from index start to end*/
function reverseArray(& $arr , $start , $end )
{
     while ( $start < $end )
     {
         $temp = $arr [ $start ];
         $arr [ $start ] = $arr [ $end ];
         $arr [ $end ] = $temp ;
         $start ++;
         $end --;
     }
}
 
// Function to
// print an array
function printArray( $arr , $size )
{
     for ( $i = 0; $i < $size ; $i ++)
     print $arr [ $i ]. " " ;
}
 
// Driver code
$arr = array (1, 2, 3, 4, 5, 6, 7);
$n = sizeof( $arr );
$d = 2;
 
// Function calling
leftRotate( $arr , $d , $n );
printArray( $arr , $n );
     
// This code is contributed
// by ChitraNayal
?>

输出：

3 4 5 6 7 1 2

时间复杂度：

上)

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