Create LetterCombPhoneNumber.java

LetterCombPhoneNumber.java

@@ -0,0 +1,37 @@
+class Solution {
+    public List<String> letterCombinations(String digits) {
+
+        if(digits.length() == 0){
+            ArrayList<String> bres = new ArrayList<String>();
+            return bres;
+        }
+        if(digits.length() == 1){
+            ArrayList<String> new_bres = new ArrayList<>();
+            char ch = digits.charAt(0);
+            String code_for_number = codes[ch - 48];
+
+        for(int i = 0; i < code_for_number.length(); i++){
+            new_bres.add("" + code_for_number.charAt(i));
+        }
+            return new_bres;
+        }
+
+        char ch = digits.charAt(0);
+        String ss = digits.substring(1);
+
+        List<String> pans = letterCombinations(ss);
+        ArrayList<String> ans = new ArrayList<String>();
+        String code_for_number = codes[ch - 48];
+
+        for(int i = 0; i < code_for_number.length(); i++){
+            char chval = code_for_number.charAt(i);
+            for(String val : pans){
+                ans.add(chval + val);
+            }
+        }
+
+        return ans;
+    }
+
+    static String[] codes = {"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
+}