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# 1055. Shortest Way to Form String

<https://leetcode.com/problems/shortest-way-to-form-string>

## Description

A **subsequence** of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., `"ace"` is a subsequence of `"abcde"` while `"aec"` is not).

Given two strings `source` and `target`, return *the minimum number of **subsequences** of* `source` *such that their concatenation equals* `target`. If the task is impossible, return `-1`.

**Example 1:**

```
**Input:** source = "abc", target = "abcbc"
**Output:** 2
**Explanation:** The target "abcbc" can be formed by "abc" and "bc", which are subsequences of source "abc".
```

**Example 2:**

```
**Input:** source = "abc", target = "acdbc"
**Output:** -1
**Explanation:** The target string cannot be constructed from the subsequences of source string due to the character "d" in target string.
```

**Example 3:**

```
**Input:** source = "xyz", target = "xzyxz"
**Output:** 3
**Explanation:** The target string can be constructed as follows "xz" + "y" + "xz".
```

**Constraints:**

* `1 <= source.length, target.length <= 1000`
* `source` and `target` consist of lowercase English letters.

## ac

```java
```


---

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