I tried to create the code to generate all possible combination of the given string in the lexicographical order:
The code that I wrote is:
void get(char *n)
{
int l=strlen(n);
sort(n,n+l);
int k=0,m,i,j,z;
while(k<l)
{
m=k;
for(i=k;i<l;i++)
{
for(j=k;j<=i;j++)
cout<<n[j];
cout<<"\n";
}
for(z=m+2;z<l;z++)
cout<<n[m]<<n[z]<<"\n";
k++;
}
}
int main()
{
char n[100];
cin>>n;
get(n);
return 0;
}
Suppose the string is : abcde
My code is not generating combinations like:
abd
abe
The output I am getting for the string abcde are:
a
ab
abc
abcd
abcde
ac
ad
ae
b
bc
bcd
bcde
bd
be
c
cd
cde
ce
d
de
e
My output does not contains strings like : abd abe
Hope this makes the question clear
How to generate all these combinations using an efficient algorithm
This is a simple recursive approach:
#include <string>
#include <iostream>
using namespace std;
void get( string str, string res ) {
cout << res << endl;
for( int i = 0; i < str.length(); i++ )
get( string(str).erase(i,1), res + str[i] );
}
int main( int argc, char **argv) {
string str = "abcde";
get( str, "" );
return 0;
}
Maybe not the most efficient way of doing it, but a short and simple one. Keep in mind, that enumerating all combinations has a complexity of O(2n) anyway. So there exists no efficient algorithm at all.