1903. Largest Odd Number in String: AC

Author: tan-wei

src/solution/mod.rs

@@ -1434,3 +1434,4 @@ mod s1898_maximum_number_of_removable_characters;
 mod s1899_merge_triplets_to_form_target_triplet;
 mod s1900_the_earliest_and_latest_rounds_where_players_compete;
 mod s1901_find_a_peak_element_ii;
+mod s1903_largest_odd_number_in_string;

src/solution/s1903_largest_odd_number_in_string.rs

@@ -0,0 +1,80 @@
+/**
+ * [1903] Largest Odd Number in String
+ *
+ * You are given a string num, representing a large integer. Return the largest-valued odd integer (as a string) that is a non-empty substring of num, or an empty string "" if no odd integer exists.
+ * A substring is a contiguous sequence of characters within a string.
+ *  
+ * Example 1:
+ *
+ * Input: num = "52"
+ * Output: "5"
+ * Explanation: The only non-empty substrings are "5", "2", and "52". "5" is the only odd number.
+ *
+ * Example 2:
+ *
+ * Input: num = "4206"
+ * Output: ""
+ * Explanation: There are no odd numbers in "4206".
+ *
+ * Example 3:
+ *
+ * Input: num = "35427"
+ * Output: "35427"
+ * Explanation: "35427" is already an odd number.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= num.length <= 10^5
+ * 	num only consists of digits and does not contain any leading zeros.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/largest-odd-number-in-string/
+// discuss: https://leetcode.com/problems/largest-odd-number-in-string/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn largest_odd_number(num: String) -> String {
+        num.as_bytes()
+            .iter()
+            .rposition(|&b| b & 1 == 1)
+            .map_or(String::new(), |p| num[..=p].to_string())
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1903_example_1() {
+        let num = "52".to_string();
+
+        let result = "5".to_string();
+
+        assert_eq!(Solution::largest_odd_number(num), result);
+    }
+
+    #[test]
+    fn test_1903_example_2() {
+        let num = "4206".to_string();
+
+        let result = "".to_string();
+
+        assert_eq!(Solution::largest_odd_number(num), result);
+    }
+
+    #[test]
+    fn test_1903_example_3() {
+        let num = "35427".to_string();
+
+        let result = "35427".to_string();
+
+        assert_eq!(Solution::largest_odd_number(num), result);
+    }
+}