### Question

Given a digit ‘3141592653’, find number of occurence of subsequence “123”. Note that the sequence occurs twice:

```
3141592653
1 2 3
1 2 3
```

Output 2.

### Solution

Refer to **[LeetCode 115] Distinct Subsequences**.

Given a digit ‘3141592653’, find number of occurence of subsequence “123”. Note that the sequence occurs twice:

```
3141592653
1 2 3
1 2 3
```

Output 2.

Refer to **[LeetCode 115] Distinct Subsequences**.