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| class Solution {
public List<String> letterCombinations(String digits) {
List<String> list = new ArrayList<String>();
if (digits.length()==0) return list;
Map<Character,String> map = new HashMap<>();
map.put('0',"");
map.put('1'," ");
map.put('2',"abc");
map.put('3',"def");
map.put('4',"ghi");
map.put('5',"jkl");
map.put('6',"mno");
map.put('7',"pqrs");
map.put('8',"tuv");
map.put('9',"wxyz");
select(digits,map,new StringBuffer(),0,list);
return list;
}
public void select(String digits,Map<Character,String> map,StringBuffer stringBuffer,int index,List<String> list){
if (index==digits.length()){
list.add(stringBuffer.toString());
}else{
char c = digits.charAt(index);
String s = map.get(c);
int len = s.length();
for (int i = 0;i<len;i++){
stringBuffer.append(s.charAt(i));
select(digits,map,stringBuffer,index+1,list);
stringBuffer.deleteCharAt(index);
}
}
}
}
|
