编写一个函数rotate（ar[]，d，n），将大小为n的arr[]旋转d个元素。
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将上述阵列旋转2将生成阵列
算法：
Initialize A = arr[0..d-1] and B = arr[d..n-1]1) Do following until size of A is equal to size of B a) If A is shorter, divide B into Bl and Br such that Br is of same length as A. Swap A and Br to change ABlBr into BrBlA. Now A is at its final place, so recur on pieces of B. b) If A is longer, divide A into Al and Ar such that Al is of same length as B Swap Al and B to change AlArB into BArAl. Now B is at its final place, so recur on pieces of A.2) Finally when A and B are of equal size, block swap them.
递归实现：
C++
#include <bits/stdc++.h> using namespace std; /*Prototype for utility functions */ void printArray( int arr[], int size); void swap( int arr[], int fi, int si, int d); void leftRotate( int arr[], int d, int n) { /* Return If number of elements to be rotated is zero or equal to array size */ if (d == 0 || d == n) return ; /* If number of elements to be rotated is more than array size*/ if (d > n) d = d % n; /*If number of elements to be rotated is exactly half of array size */ if (n - d == d) { swap(arr, 0, n - d, d); return ; } /* If A is shorter*/ if (d < n - d) { swap(arr, 0, n - d, d); leftRotate(arr, d, n - d); } else /* If B is shorter*/ { swap(arr, 0, d, n - d); leftRotate(arr + n - d, 2 * d - n, d); /*This is tricky*/ } } /*UTILITY FUNCTIONS*/ /* function to print an array */ void printArray( int arr[], int size) { int i; for (i = 0; i < size; i++) cout << arr[i] << " " ; cout << endl; } /*This function swaps d elements starting at index fi with d elements starting at index si */ void swap( int arr[], int fi, int si, int d) { int i, temp; for (i = 0; i < d; i++) { temp = arr[fi + i]; arr[fi + i] = arr[si + i]; arr[si + i] = temp; } } // Driver Code int main() { int arr[] = {1, 2, 3, 4, 5, 6, 7}; leftRotate(arr, 2, 7); printArray(arr, 7); return 0; } // This code is contributed by rathbhupendra |
C
#include<stdio.h> /*Prototype for utility functions */ void printArray( int arr[], int size); void swap( int arr[], int fi, int si, int d); void leftRotate( int arr[], int d, int n) { /* Return If number of elements to be rotated is zero or equal to array size */ if (d == 0 || d == n) return ; /*If number of elements to be rotated is exactly half of array size */ if (n-d == d) { swap(arr, 0, n-d, d); return ; } /* If A is shorter*/ if (d < n-d) { swap(arr, 0, n-d, d); leftRotate(arr, d, n-d); } else /* If B is shorter*/ { swap(arr, 0, d, n-d); leftRotate(arr+n-d, 2*d-n, d); /*This is tricky*/ } } /*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]); printf ( " " ); } /*This function swaps d elements starting at index fi with d elements starting at index si */ void swap( int arr[], int fi, int si, int d) { int i, temp; for (i = 0; i<d; i++) { temp = arr[fi + i]; arr[fi + i] = arr[si + i]; arr[si + i] = temp; } } /* Driver program to test above functions */ int main() { int arr[] = {1, 2, 3, 4, 5, 6, 7}; leftRotate(arr, 2, 7); printArray(arr, 7); getchar (); return 0; } |
JAVA
import java.util.*; class GFG { // Wrapper over the recursive function leftRotateRec() // It left rotates arr[] by d. public static void leftRotate( int arr[], int d, int n) { leftRotateRec(arr, 0 , d, n); } public static void leftRotateRec( int arr[], int i, int d, int n) { /* Return If number of elements to be rotated is zero or equal to array size */ if (d == 0 || d == n) return ; /*If number of elements to be rotated is exactly half of array size */ if (n - d == d) { swap(arr, i, n - d + i, d); return ; } /* If A is shorter*/ if (d < n - d) { swap(arr, i, n - d + i, d); leftRotateRec(arr, i, d, n - d); } else /* If B is shorter*/ { swap(arr, i, d, n - d); leftRotateRec(arr, n - d + i, 2 * d - n, d); /*This is tricky*/ } } /*UTILITY FUNCTIONS*/ /* function to print an array */ public static void printArray( int arr[], int size) { int i; for (i = 0 ; i < size; i++) System.out.print(arr[i] + " " ); System.out.println(); } /*This function swaps d elements starting at index fi with d elements starting at index si */ public static void swap( int arr[], int fi, int si, int d) { int i, temp; for (i = 0 ; i < d; i++) { temp = arr[fi + i]; arr[fi + i] = arr[si + i]; arr[si + i] = temp; } } // Driver Code public static void main (String[] args) { int arr[] = { 1 , 2 , 3 , 4 , 5 , 6 , 7 }; leftRotate(arr, 2 , 7 ); printArray(arr, 7 ); } } // This code is contributed by codeseeker |
Python3
# Wrapper over the recursive function leftRotateRec() # It left rotates arr by d. def leftRotate(arr, d, n): leftRotateRec(arr, 0 , d, n); def leftRotateRec(arr, i, d, n): ''' * Return If number of elements to be rotated is zero or equal to array size ''' if (d = = 0 or d = = n): return ; ''' * If number of elements to be rotated is exactly half of array size ''' if (n - d = = d): swap(arr, i, n - d + i, d); return ; ''' If A is shorter ''' if (d < n - d): swap(arr, i, n - d + i, d); leftRotateRec(arr, i, d, n - d); ''' If B is shorter ''' else : swap(arr, i, d, n - d); ''' This is tricky ''' leftRotateRec(arr, n - d + i, 2 * d - n, d); ''' UTILITY FUNCTIONS ''' ''' function to print an array ''' def printArray(arr, size): for i in range (size): print (arr[i], end = " " ); print (); ''' * This function swaps d elements starting at * index fi with d elements starting at index si ''' def swap(arr, fi, si, d): for i in range (d): temp = arr[fi + i]; arr[fi + i] = arr[si + i]; arr[si + i] = temp; # Driver Code if __name__ = = '__main__' : arr = [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]; leftRotate(arr, 2 , 7 ); printArray(arr, 7 ); # This code is contributed by Rohit_ranjan |
C#
using System; class GFG{ // Wrapper over the recursive function // leftRotateRec() // It left rotates []arr by d. public static void leftRotate( int []arr, int d, int n) { leftRotateRec(arr, 0, d, n); } public static void leftRotateRec( int []arr, int i, int d, int n) { // Return If number of elements // to be rotated is zero or equal // to array size if (d == 0 || d == n) return ; // If number of elements to be rotated // is exactly half of array size if (n - d == d) { swap(arr, i, n - d + i, d); return ; } // If A is shorter if (d < n - d) { swap(arr, i, n - d + i, d); leftRotateRec(arr, i, d, n - d); } // If B is shorter else { swap(arr, i, d, n - d); // This is tricky leftRotateRec(arr, n - d + i, 2 * d - n, d); } } // UTILITY FUNCTIONS // Function to print an array public static void printArray( int []arr, int size) { int i; for (i = 0; i < size; i++) Console.Write(arr[i] + " " ); Console.WriteLine(); } // This function swaps d elements // starting at index fi with d elements // starting at index si public static void swap( int []arr, int fi, int si, int d) { int i, temp; for (i = 0; i < d; i++) { temp = arr[fi + i]; arr[fi + i] = arr[si + i]; arr[si + i] = temp; } } // Driver Code public static void Main(String[] args) { int []arr = { 1, 2, 3, 4, 5, 6, 7 }; leftRotate(arr, 2, 7); printArray(arr, 7); } } // This code is contributed by amal kumar choubey |
Javascript
<script> let leftRotate = (arr, d, n) =>{ /* Return If number of elements to be rotated is zero or equal to array size */ if (d == 0 || d == n) return ; /*If number of elements to be rotated is exactly half of array size */ if (n - d == d) { arr = swap(arr, 0, n - d, d); return ; } /* If A is shorter*/ if (d < n - d) { arr = swap(arr, 0, n - d, d); leftRotate(arr, d, n - d); } else { /* If B is shorter*/ arr = swap(arr, 0, d, n - d); /*This is tricky*/ leftRotate(arr + n - d, 2 * d - n, d); } } /*UTILITY FUNCTIONS*/ /* function to print an array */ let printArray = (arr, size) =>{ ans = '' for (let i = 0; i < size; i++) ans += arr[i]+ " " ; document.write(ans) } /*This function swaps d elements starting at index fi with d elements starting at index si */ let swap = (arr, fi, si, d) =>{ for (let i = 0; i < d; i++) { let temp = arr[fi + i]; arr[fi + i] = arr[si + i]; arr[si + i] = temp; } return arr } // Driver Code arr = [1, 2, 3, 4, 5, 6, 7]; leftRotate(arr, 2, 7); printArray(arr, 7); </script> |
输出
3 4 5 6 7 1 2
迭代实现： 下面是同一算法的迭代实现。这里使用了相同的实用程序函数swap（）。
C++
// C++ code for above implementation void leftRotate( int arr[], int d, int n) { int i, j; if (d == 0 || d == n) return ; /* If number of elements to be rotated is more than array size*/ if (d > n) d = d % n; i = d; j = n - d; while (i != j) { if (i < j) /*A is shorter*/ { swap(arr, d - i, d + j - i, i); j -= i; } else /*B is shorter*/ { swap(arr, d - i, d, j); i -= j; } // printArray(arr, 7); } /*Finally, block swap A and B*/ swap(arr, d - i, d, i); } // This code is contributed by Shivani |
C
// C code for above implementation void leftRotate( int arr[], int d, int n) { int i, j; if (d == 0 || d == n) return ; /* If number of elements to be rotated is more than array size*/ if (d > n) d = d % n; i = d; j = n - d; while (i != j) { if (i < j) /*A is shorter*/ { swap(arr, d-i, d+j-i, i); j -= i; } else /*B is shorter*/ { swap(arr, d-i, d, j); i -= j; } // printArray(arr, 7); } /*Finally, block swap A and B*/ swap(arr, d-i, d, i); } |
JAVA
//Java code for above implementation static void leftRotate( int arr[], int d, int n) { int i, j; if (d == 0 || d == n) return ; /* If number of elements to be rotated is more than array size*/ if (d > n) d = d % n; i = d; j = n - d; while (i != j) { if (i < j) /*A is shorter*/ { swap(arr, d-i, d+j-i, i); j -= i; } else /*B is shorter*/ { swap(arr, d-i, d, j); i -= j; } // printArray(arr, 7); } /*Finally, block swap A and B*/ swap(arr, d-i, d, i); } |
Python3
# Python3 code for above implementation def leftRotate(arr, d, n): if (d = = 0 or d = = n): return ; i = d j = n - d while (i ! = j): if (i < j): # A is shorter swap(arr, d - i, d + j - i, i) j - = i else : # B is shorter swap(arr, d - i, d, j) i - = j swap(arr, d - i, d, i) # This code is contributed # by Adarsh_Verma |
C#
// C# code for above implementation static void leftRotate( int []arr, int d, int n) { int i, j; if (d == 0 || d == n) return ; /* If number of elements to be rotated is more than array size*/ if (d > n) d = d % n; i = d; j = n - d; while (i != j) { if (i < j) /*A is shorter*/ { swap(arr, d-i, d+j-i, i); j -= i; } else /*B is shorter*/ { swap(arr, d-i, d, j); i -= j; } } /*Finally, block swap A and B*/ swap(arr, d-i, d, i); } // This code is contributed by Rajput-Ji |
Javascript
<script> // JavaScript code for above implementation function leftRotate(arr, d, n) { if (d == 0 || d == n) return ; let i = d; let j = n - d; while (i != j) { if (i < j) { // A is shorter arr = swap(arr, d - i, d + j - i, i); j -= i; } else { // B is shorter arr = swap(arr, d - i, d, j); i -= j; } } arr = swap(arr, d - i, d, i); // This code is contributed by rohitsingh04052. } </script> |
时间复杂性： O（n） 有关数组旋转的其他方法，请参见以下帖子： https://www.geeksforgeeks.org/array-rotation/ https://www.geeksforgeeks.org/program-for-array-rotation-continued-reversal-algorithm/
参考资料： http://www.cs.bell-labs.com/cm/cs/pearls/s02b.pdf 如果您在上述程序/算法中发现任何错误，或希望共享有关块交换算法的任何其他信息，请写评论。
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