C++ Program to Generate a Sequence of N Characters for a Given Specific Case

This is a C++ Program to generate a sequence of n characters for a given specific case.

1. This algorithm generates sequences of n characters from a specific sequence.
2. The time complexity of this algorithm is O(n).

1. This algorithm takes the input of the specific sequence.
2. It generates a random subsequence from the given character string.
3. Exit.

C++ Program to generate a sequence of n characters for a given specific case.
This program is successfully run on Dev-C++ using TDM-GCC 4.9.2 MinGW compiler on a Windows system.

#include<iostream>
#include<stdlib.h>
#include<string.h>
 
using namespace std;
 
// A function to generate a random sequence of the given length from a given string.
void GenSequence(char str[], int m, int len, char *seq)
{
	int i, j=0, k, index;
	for(i = 0; i < m; i++)
	{
		// Use rand() to generate random indexes.
		// Store the very first character directly into the sequence.
		if(j == 0)
			seq[j++] = str[rand()%len];
		// Check for the repetitions.
		else
		{
			h:
			index = rand()%len;
			for(k = 0; k < j; k++)
			{
				if(str[index] == seq[k])
					goto h;
			}
			seq[j++] = str[index];
		}
	}
	// End the sequence with null character.
	seq[j] = '\0';
}
 
int main()
{
	int n, m, len, i;
	char str[100];
	cout<<"Enter the base string: ";
	cin>>str;
 
	cout<<"\nEnter the number of strings to be generated from the Base string: ";
	cin>>n;
 
	cout<<"\nEnter the length of each string to be generated: ";
	cin>>m;
 
	len = strlen(str);
 
	// Print the generated sequence.
	for(i = 0; i < n; i++)
	{
		char seq[m];
		GenSequence(str, m, len, seq);
		cout<<"\nSequence "<<i+1<<": "<<seq;
	}
 
	return 0;
}

1. Take the input of the base string, the number of the sequences to be generated and the length of each sequence.
2. Using strlen() library function, get the length of the base sequence.
3. Call GenSequence() n times for n sequence.
4. Inside GenSequence(), using rand() generate the random index for each character in the required sequence.
5. Check if that sequence is used earlier if it is, then it discards that and generate random index again.
6. Return to main and display the generated sequence.
7. Exit.

Case 1:
Enter the base string: abcedfghijklmnopq
 
Enter the number of strings to be generated from the Base string: 5
 
Enter the length of each string to be generated: 6
 
Sequence 1: hfkoqe
Sequence 2: qabkio
Sequence 3: qpeing
Sequence 4: bjaegn
Sequence 5: qpfham
 
Case 2:
Enter the base string: aabbccddeeffgghhiijj
 
Enter the number of strings to be generated from the Base string: 5
 
Enter the length of each string to be generated: 8
 
Sequence 1: ahaecjbc
Sequence 2: cdfhbicg
Sequence 3: gaijhddf
Sequence 4: jgdjhhbf
Sequence 5: bcafedbi

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