 # Print all sub sequences of a given array

Objec­tive:  Given an array write an algorithm to print all the possible sub subsequences.

Example:

```int [] a = {1, 2, 3};
Output: Possible sub sequences –
{Empty}, {1}, {2}, {3}, {1, 2} ,{1,3}, {2, 3}, {1, 2, 3}
```

Approach:

• The approach will be similar to as discussed here Gen­er­ate All Strings of n bits
• If we consider n= 3(same as the array size) then all possible combinations are [0, 0, 0] [1, 0, 0] [0, 1, 0] [1, 1, 0] [0, 0, 1] [1, 0, 1] [0, 1, 1] [1, 1, 1].
• So from the above combinations, wherever the bit is set to 1, place an array element at the position and wherever the bit is set to 0, ignore the array element.
• The above step will give the desired result.
• See the code below for better understanding.

Time Complexity: O(2^n)

Complete Code:

Output:

```1 2 3
1 2
1 3
1
2 3
2
3
{Empty Set}```

### 1 thought on “Print all sub sequences of a given array”

1. Much simpler code

public class ArraySubSequences {

public static void main(String[] args) {

int[] a = {1,2,3};

printSubSequences(a, 0, new ArrayList(), ” “);

}

static void printSubSequences(int[] arr, int start, List chosen, String space) {

if(start > arr.length) {
return;
}
else {
for (int i = start; i < arr.length; i++) {
//choose