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| import java.util.Arrays;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
public class LetterCombinationsofaPhoneNumber {
public List<String> letterCombinations(String digits) {
HashMap<Character, char[]> m = new HashMap<>();
m.put('2', new char[] {'a', 'b','c'});
m.put('3', new char[] {'d','e','f'});
m.put('4', new char[] {'g','h','i'});
m.put('5', new char[] {'j','k','l'});
m.put('6', new char[] {'m','n','o'});
m.put('7', new char[] {'p','q','r','s'});
m.put('8', new char[] {'t','u','v'});
m.put('9', new char[] {'w','x','y','z'});
List<String> ans = new LinkedList<>();
dfs(ans, digits, "", m);
return ans;
}
public void dfs(List<String> ans, String digits, String t, HashMap<Character, char[]> m) {
if (digits.isEmpty()) {
ans.add(t);
}
for (char i: m.get(digits.charAt(0))) {
dfs(ans, digits.substring(1), t+i, m);
}
}
public static void main(String[] args) {
}
}
|
