# 阵列旋转的逆向算法

2021年3月9日16:08:06 发表评论 726 次浏览

## 本文概述

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

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

• 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。

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]

## 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
?>

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