leetcode

commit 838ae094d71ebac895404c4c0dfe1d016b475555
parent 6a8a8d85c3f9104ece8ede5041a2fee2f0977bf6
Author: AndrewLockVI <andrewlaack1@gmail.com>
Date:   Mon, 22 May 2023 08:44:37 -0500

Completed letter combination of a phone number problem using a hashmap, recursion, backtracking, and dart.

Diffstat:
A
letter-combinations-of-a-phone-number/letter-combinations-of-a-phone-number.dart
 | 
43
+++++++++++++++++++++++++++++++++++++++++++

1 file changed, 43 insertions(+), 0 deletions(-)
diff --git a/letter-combinations-of-a-phone-number/letter-combinations-of-a-phone-number.dart b/letter-combinations-of-a-phone-number/letter-combinations-of-a-phone-number.dart
@@ -0,0 +1,43 @@
+//Given a list of numbers return all possible permutations that could result from the given inputs assuming that
+//each number can be any of the associated letters when looking at an old phone where you can access letters by
+//repeating numbers.
+//Time: 247ms Beats: 77.78%
+//Memory: 141MB Beats: 38.89%
+
+class Solution {
+  Map<int , List<String>> options = {};
+  int original_length = -1;
+  Solution(){
+      options = {
+          2 : ["a" , "b" , "c"],
+          3 : ["d" , "e" , "f"],
+          4 : ["g" , "h" , "i"],
+          5 : ["j" , "k" , "l"],
+          6 : ["m" , "n" , "o"],
+          7 : ["p" , "q" , "r" , "s"],
+          8 : ["t" , "u" , "v"],
+          9 : ["w" , "x" , "y" , "z"]
+      };
+  }
+  List<String> letterCombinations(String digits) {
+    if(original_length == -1){
+        original_length = digits.length;
+        if(digits.length == 0){
+            return [];
+        }
+    }
+    if(digits.length == 0){
+        return [""];
+    }
+    List<String> ret_list = [];
+    String new_digits = digits.substring(1);
+    List<String> vals = (options[int.parse(digits[0])] ?? []);
+    for(int x = 0 ; x < vals.length ; ++x){
+        List<String> returned_list = letterCombinations(new_digits);
+        for(int y = 0 ; y < returned_list.length ; ++y){
+            ret_list.add(vals[x] + returned_list[y]);
+        }
+    }
+      return ret_list;
+  }
+}