Create 0017-letter-combinations-of-a-phone-number.rs

Author: nirajvenkat

rust/0017-letter-combinations-of-a-phone-number.rs

@@ -0,0 +1,37 @@
+use std::collections::HashMap;
+
+impl Solution {
+    fn backtrack(i: usize, curr_str: String, result: &mut Vec<String>, digits: &String, d_c_map: &HashMap<char, &str>) {
+        if curr_str.len() == digits.len() {
+            result.push(curr_str);
+            return;
+        }
+        
+        let letters = d_c_map.get(&digits.chars().nth(i).unwrap()).unwrap().to_string();
+        for ch in letters.chars() {
+            let mut append_str = curr_str.clone();
+            append_str.push(ch);
+            Self::backtrack(i + 1, append_str, result, digits, d_c_map);
+        }
+    }
+
+    pub fn letter_combinations(digits: String) -> Vec<String> {
+        let mut result = vec![];
+        let d_c_map = HashMap::from([
+            ('2', "abc"),
+            ('3', "def"),
+            ('4', "ghi"),
+            ('5', "jkl"),
+            ('6', "mno"),
+            ('7', "qprs"),
+            ('8', "tuv"),
+            ('9', "wxyz"),
+        ]);
+
+        if !digits.is_empty() {
+            Solution::backtrack(0, "".to_string(), &mut result, &digits, &d_c_map);
+        }
+
+        result
+    }
+}