Sync LeetCode submission Runtime - 0 ms (100.00%), Memory - 17.7 MB (23.23%)

Author: jimit105

0065-valid-number/README.md

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+<p>Given a string <code>s</code>, return whether <code>s</code> is a <strong>valid number</strong>.<br />
+<br />
+For example, all the following are valid numbers: <code>&quot;2&quot;, &quot;0089&quot;, &quot;-0.1&quot;, &quot;+3.14&quot;, &quot;4.&quot;, &quot;-.9&quot;, &quot;2e10&quot;, &quot;-90E3&quot;, &quot;3e+7&quot;, &quot;+6e-1&quot;, &quot;53.5e93&quot;, &quot;-123.456e789&quot;</code>, while the following are not valid numbers: <code>&quot;abc&quot;, &quot;1a&quot;, &quot;1e&quot;, &quot;e3&quot;, &quot;99e2.5&quot;, &quot;--6&quot;, &quot;-+3&quot;, &quot;95a54e53&quot;</code>.</p>
+
+<p>Formally, a&nbsp;<strong>valid number</strong> is defined using one of the following definitions:</p>
+
+<ol>
+	<li>An <strong>integer number</strong> followed by an <strong>optional exponent</strong>.</li>
+	<li>A <strong>decimal number</strong> followed by an <strong>optional exponent</strong>.</li>
+</ol>
+
+<p>An <strong>integer number</strong> is defined with an <strong>optional sign</strong> <code>&#39;-&#39;</code> or <code>&#39;+&#39;</code> followed by <strong>digits</strong>.</p>
+
+<p>A <strong>decimal number</strong> is defined with an <strong>optional sign</strong> <code>&#39;-&#39;</code> or <code>&#39;+&#39;</code> followed by one of the following definitions:</p>
+
+<ol>
+	<li><strong>Digits</strong> followed by a <strong>dot</strong> <code>&#39;.&#39;</code>.</li>
+	<li><strong>Digits</strong> followed by a <strong>dot</strong> <code>&#39;.&#39;</code> followed by <strong>digits</strong>.</li>
+	<li>A <strong>dot</strong> <code>&#39;.&#39;</code> followed by <strong>digits</strong>.</li>
+</ol>
+
+<p>An <strong>exponent</strong> is defined with an <strong>exponent notation</strong> <code>&#39;e&#39;</code> or <code>&#39;E&#39;</code> followed by an <strong>integer number</strong>.</p>
+
+<p>The <strong>digits</strong> are defined as one or more digits.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">s = &quot;0&quot;</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">true</span></p>
+</div>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">s = &quot;e&quot;</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">false</span></p>
+</div>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">s = &quot;.&quot;</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">false</span></p>
+</div>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= s.length &lt;= 20</code></li>
+	<li><code>s</code> consists of only English letters (both uppercase and lowercase), digits (<code>0-9</code>), plus <code>&#39;+&#39;</code>, minus <code>&#39;-&#39;</code>, or dot <code>&#39;.&#39;</code>.</li>
+</ul>

0065-valid-number/solution.py

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+# Approach 1: Follow The Rules!
+
+# Time: O(n)
+# Space: O(1)
+
+class Solution:
+    def isNumber(self, s: str) -> bool:
+        seen_digit = seen_exponent = seen_dot = False
+
+        for i, c in enumerate(s):
+            if c.isdigit():
+                seen_digit = True
+            elif c in ['+', '-']:
+                if i > 0 and s[i - 1] not in ['e', 'E']:
+                    return False
+            elif c in ['e', 'E']:
+                if seen_exponent or not seen_digit:
+                    return False
+                seen_exponent = True
+                seen_digit = False
+            elif c == '.':
+                if seen_dot or seen_exponent:
+                    return False
+                seen_dot = True
+
+            # Invalid character
+            else:
+                return False
+        
+        # Must have at least one number and number after 'e'/'E' if exists
+        return seen_digit
+