Sync LeetCode submission Runtime - 95 ms (97.56%), Memory - 17.8 MB (81.26%)

Author: jimit105

2998---count-symmetric-integers/README.md

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+<p>You are given two positive integers <code>low</code> and <code>high</code>.</p>
+
+<p>An integer <code>x</code> consisting of <code>2 * n</code> digits is <strong>symmetric</strong> if the sum of the first <code>n</code> digits of <code>x</code> is equal to the sum of the last <code>n</code> digits of <code>x</code>. Numbers with an odd number of digits are never symmetric.</p>
+
+<p>Return <em>the <strong>number of symmetric</strong> integers in the range</em> <code>[low, high]</code>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> low = 1, high = 100
+<strong>Output:</strong> 9
+<strong>Explanation:</strong> There are 9 symmetric integers between 1 and 100: 11, 22, 33, 44, 55, 66, 77, 88, and 99.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> low = 1200, high = 1230
+<strong>Output:</strong> 4
+<strong>Explanation:</strong> There are 4 symmetric integers between 1200 and 1230: 1203, 1212, 1221, and 1230.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= low &lt;= high &lt;= 10<sup>4</sup></code></li>
+</ul>

2998---count-symmetric-integers/solution.py

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+# Approach 1: Enumeration
+
+# Time: O(high - low)
+# Space: O(1)
+
+class Solution:
+    def countSymmetricIntegers(self, low: int, high: int) -> int:
+        res = 0
+
+        for x in range(low, high + 1):
+            if x < 100 and x % 11 == 0:
+                res += 1
+            if 1000 <= x < 10000:
+                left = x // 1000 + x % 1000 // 100
+                right = x % 100 // 10 + x  % 10
+                if left == right:
+                    res += 1
+        return res
+