题目：

题解：

func diffOne(s, t string) (diff bool) {for i := range s {if s[i] != t[i] {if diff {return false}diff = true}}return
}func minMutation(start, end string, bank []string) int {if start == end {return 0}m := len(bank)adj := make([][]int, m)endIndex := -1for i, s := range bank {if s == end {endIndex = i}for j := i + 1; j < m; j++ {if diffOne(s, bank[j]) {adj[i] = append(adj[i], j)adj[j] = append(adj[j], i)}}}if endIndex == -1 {return -1}var q []intvis := make([]bool, m)for i, s := range bank {if diffOne(start, s) {q = append(q, i)vis[i] = true}}for step := 1; q != nil; step++ {tmp := qq = nilfor _, cur := range tmp {if cur == endIndex {return step}for _, nxt := range adj[cur] {if !vis[nxt] {vis[nxt] = trueq = append(q, nxt)}}}}return -1
}