Solve valid-number.

source/lib.rs

@@ -18,6 +18,7 @@ pub mod roman_to_integer;
 pub mod set_mismatch;
 pub mod two_sum;
 pub mod valid_anagram;
+pub mod valid_number;
 pub mod valid_palindrome;
 pub mod valid_parenthesis;
 pub mod word_pattern;

source/valid_number/mod.rs

@@ -0,0 +1,23 @@
+pub fn is_number(string: String) -> bool {
+  let string = string.to_lowercase();
+
+  if string.contains("inf") || string.contains("nan") {
+    return false;
+  }
+
+  let mut parts = string.split("e");
+
+  let valid_significand = match parts.next() {
+    Some(part) => part.parse::<f64>().is_ok(),
+    None => unreachable!(),
+  };
+
+  let valid_exponent = match parts.next() {
+    Some(part) => part.parse::<isize>().is_ok(),
+    None => true,
+  };
+
+  let nothing_remaining = parts.next().is_none();
+
+  valid_significand && valid_exponent && nothing_remaining
+}

tests/valid_number.rs

@@ -0,0 +1,13 @@
+use leetcode::valid_number::is_number;
+
+use test_case::test_case;
+
+#[test_case("0", true; "example 1")]
+#[test_case("e", false; "example 2")]
+#[test_case(".", false; "example 3")]
+#[test_case("-inf", false; "infinity")]
+#[test_case("NaN", false; "not a number")]
+#[test_case("", false; "empty")]
+fn test_valid_number(input: &str, expected: bool) {
+  assert_eq!(is_number(input.to_string()), expected);
+}