阵列旋转的逆向算法 _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]

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将上面的数组旋转2将使数组

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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++ 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# 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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