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| // @Title: 电话号码的字母组合 (Letter Combinations of a Phone Number)
// @Author: 15816537946@163.com
// @Date: 2020-10-30 09:14:48
// @Runtime: 0 ms
// @Memory: 2 MB
func letterCombinations(digits string) []string {
if len(digits) == 0 {
return nil
}
phoneMap := map[int][]string{
2: []string{
"a", "b", "c",
},
3: []string{
"d", "e", "f",
},
4: []string{
"g", "h", "i",
},
5: []string{
"j", "k", "l",
},
6: []string{
"m", "n", "o",
},
7: []string{
"p", "q", "r", "s",
},
8: []string{
"t", "u", "v",
},
9: []string{
"w", "x", "y", "z",
},
}
ans := make([]string, 0)
var backtrack func(string, []byte)
backtrack = func(out string, idx []byte) {
if len(idx) == 0 {
tmp := out
ans = append(ans, tmp)
return
}
for _, letters := range phoneMap[int(idx[0]-'0')] {
for _, letter := range letters {
backtrack(out+string(letter), idx[1:])
}
}
}
backtrack("", []byte(digits))
return ans
}
|