题目:
给定一个仅包含数字 2-9 的字符串，返回所有它能表示的字母组合。
给出数字到字母的映射如下（与电话按键相同）。注意 1 不对应任何字母。
编辑
示例:
- 输入："23"
- 输出：["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
说明：尽管上面的答案是按字典序排列的，但是你可以任意选择答案输出的顺序。
java:
static List list = new ArrayList();
static StringBuilder builder = new StringBuilder();
public static List<String> letterCombinations(String array) {
if (array == null || array.length() == 0) {
return list;
}
//初始对应所有的数字，为了直接对应2-9，新增了两个无效的字符串""
String[] numString = {"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
backTracking(array, numString, 0);
return list;
}
private static void backTracking(String array, String[] numString, int num) {
if (num == array.length()) {
list.add(builder.toString());
return;
}
String str = numString[array.charAt(num) - '0'];
for (int i = 0; i < str.length(); i++) {
builder.append(str.charAt(i));
backTracking(array, numString, num + 1);
builder.deleteCharAt(builder.length() - 1);
}
}
public static void main(String[] args) {
List<String> list = letterCombinations("23");
for (String s : list) {
System.out.println(s);
}
}
}
Go:
import "fmt"
var (
m []string
path = make([]byte, 0)
res = make([]string, 0)
)
func LetterCombinations(array string) []string {
m = []string{"abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"}
if array == "" {
return res
}
dfs(array, 0)
return res
}
func dfs(array string, start int) {
if len(path) == len(array) {
tmp := string(path)
fmt.Println(tmp)
res = append(res, tmp)
return
}
digit := int(array[start] - '0')
str := m[digit-2]
for i := 0; i < len(str); i++ {
path = append(path, str[i])
fmt.Println(path)
dfs(array, start+1)
path = path[:len(path)-1]
}
}
func main() {
str := "23"
combinations := LeetCode.LetterCombinations(str)
fmt.Println(combinations)
}
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