A gene string can be represented by an 8-character long string, with choices from "A", "C", "G", "T".
Suppose we need to investigate about a mutation (mutation from "start" to "end"), where ONE mutation is defined as ONE single character changed in the gene string.
For example, "AACCGGTT" -> "AACCGGTA" is 1 mutation.
Also, there is a given gene "bank", which records all the valid gene mutations. A gene must be in the bank to make it a valid gene string.
Now, given 3 things - start, end, bank, your task is to determine what is the minimum number of mutations needed to mutate from "start" to "end". If there is no such a mutation, return -1.
Note:
- Starting point is assumed to be valid, so it might not be included in the bank.
- If multiple mutations are needed, all mutations during in the sequence must be valid.
- You may assume start and end string is not the same.
Example 1:
start: "AACCGGTT"
end: "AACCGGTA"
bank: ["AACCGGTA"]
return: 1
Example 2:
start: "AACCGGTT"
end: "AAACGGTA"
bank: ["AACCGGTA", "AACCGCTA", "AAACGGTA"]
return: 2
Example 3:
start: "AAAAACCC"
end: "AACCCCCC"
bank: ["AAAACCCC", "AAACCCCC", "AACCCCCC"]
return: 3
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