Given a List of N Strings, generate and print all possible combinations of R elements in array and return X random combinations from the result. Following is the code for implementing it:
K random combinations of N elements in List in Java
Combinations of a String
Problem:
Write an algorithm to print all possible combinations of characters in a string.
Solution:
Since we need to generate combinations, we can start with a single character and then continue to add a character to combinations we have seen so far.
Let’s use “XYZ” as an example.
public void buildTree(String input, StringBuffer output, int k)
{
for (int i = k; i < input.length(); i++)
{
output.append(input.charAt(i));
buildTree(input, output, i + 1);
output.deleteCharAt(output.length() - 1);
}
}
public static void main(String[] args){
buildTree("XYZ", new StringBuffer(), 0);
}
Dry Run just to give an idea:
X–>Y–>Z
–>Z–>YY–>X–>Z
–>Z–>XZ–>Y–>X
–>X–>Y