Normal and cyclic shifts of arrays in C ++

Normal shift:

If you want to shift n digits from the last position of an array to the right, the first position of the array is shifted to the right.

The procedure is as follows:

View code

# Include <iostream>
# Include <stdlib. h>
Using namespace STD;
Int s [11] = {1, 2, 4, 5, 6, 7, 8, 9, 0 };
Void main ()
{
For (INT I = 0; I <11; I ++)
{
Cout <s [I];
}
Cout <Endl;
// Shift code, which is assumed to shift to the right
For (Int J = 10; j> 0; j --)
{
S [J] = s [J-1];
}
For (int K = 0; k <11; k ++)
{
Cout <s [k];
}
Cout <Endl;
}

Program running result:

　　

Cyclic shift:

View code

# Include <iostream>
# Include <stdlib. h>
Using namespace STD;
Int s [10] = {1, 2, 4, 5, 6, 7, 8, 9, 0 };
Void main ()
{
Int temp;
// Shifts three places to the right of the loop
For (INT I = 1; I <= 3; I ++)
{
Temp = s [9];
For (Int J = 9; j> = 1; j --)
{
S [J] = s [J-1];
}
S [0] = temp;
}
For (int K = 0; k <= 9; k ++)
{
Cout <s [k];
}
}

In fact, the principle is to shift the array through an indirect variable. Assume that the array length is n and the number of shifts to the right needs to be shifted K times. The complexity of the algorithm is O (K * n ), when K> N, the algorithm complexity is even greater than O (N ^ 2 ).

Running result diagram:

Through analysis, we can find that K> N is the same as k' = K % N, and the following algorithm is derived:

View code

# Include <iostream>
# Include <stdlib. h>
Using namespace STD;
Int s [10] = {1, 2, 4, 5, 6, 7, 8, 9, 0 };
Void main ()
{
Int temp;
Int K, KK;
K = 99;
// Shift K bits to the right
Kk = K % 10; // The array length is 10
For (INT I = 1; I <= K; I ++)
{
Temp = s [9];
For (Int J = 9; j> = 1; j --)
{
S [J] = s [J-1];
}
S [0] = temp;
}
For (int K = 0; k <= 9; k ++)
{
Cout <s [k];
}
Cout <Endl;
}

The running result is omitted.

Find an O (n) method on the Internet. The principle is as follows:

Assume that the original order column is abcd1234.

After the four-digit shift, the value is 1234 ABCD.

The shift process can be expressed as follows:

Sort ABCD in reverse order: dcba1234

Sort in reverse order 1234: dcba4321

Forward dcba4321: 1234 ABCD

That is to say, you need to write a reverse function and perform a cubic reverse transformation.

The Code is as follows:

View code

1 # include <iostream>
2 # include <stdlib. h>
3 using namespace STD;
4 void reverse (int * arr, int B, int e );
5 Int s [10] = {1, 2, 4, 5, 6, 7, 8, 9, 0 };
6 void main ()
7 {
8 int K, KK, N;
9 N = 10;
10 K = 99;
11 KK = K % 10;
12 // The following is the cyclic shift part.
13 reverse (S, 0, N-kk-1 );
14 reverse (S, N-KK, N-1 );
15 reverse (S, 0, N-1 );
16 // display
17 For (INT I = 0; I <= 9; I ++)
18 {
19 cout <s [I];
20}
21 cout <Endl;
22}
23 void reverse (int * arr, int B, int e)
24 {
25 int temp;
26 For (; B <E; B ++, e --)
27 {
28 temp = arr [E];
29 arr [e] = arr [B];
30 arr [B] = temp;
31}
32}