AllAdjacentCombination.java

package com.interview.recursion;

/**
 * Generate all combination of size k and less of adjacent numbers
 * e.g 1,2,3,4 k = 2
 * 1 2 3 4
 * 12 3 4
 * 1 23 4
 * 1 2 3 34
 * 12 34
 * @author tusroy
 *
 */
public class AllAdjacentCombination {

    public void combination(int input[],int result[],int k,int pos,int r){
        
        if(pos == input.length){
            for(int i=0; i < r ; i++){
                System.out.print(result[i] + " ");
            }
            System.out.println();
            return;
        }
        for(int i=pos; i < pos + k && i < input.length; i++ ){
            result[r] = formNumber(input,pos,i);
            combination(input,result,k,i+1,r+1);
        }
    }
    
    private int formNumber(int input[], int start, int end){
        int num = 0;
        for(int i=start; i <=end; i++){
            num = num*10 + input[i];
        }
        return num;
    }
     
    public static void main(String args[]){
        AllAdjacentCombination adc = new AllAdjacentCombination();
        int input[] = {1,2,3,4,5};
        int result[] = new int[input.length];
        adc.combination(input,result,3,0,0);
    }
}