Sync LeetCode submission Runtime - 703 ms (5.02%), Memory - 9.2 MB (10.39%)

Author: koralkulacoglu

LeetCode/4245-count-commas-in-range/README.md

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+<p>You are given an integer <code>n</code>.</p>
+
+<p>Return the <strong>total</strong> number of commas used when writing all integers from <code>[1, n]</code> (inclusive) in <strong>standard</strong> number formatting.</p>
+
+<p>In <strong>standard</strong> formatting:</p>
+
+<ul>
+	<li>A comma is inserted after <strong>every three</strong> digits from the right.</li>
+	<li>Numbers with <strong>fewer</strong> than 4 digits contain no commas.</li>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">n = 1002</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">3</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>The numbers <code>&quot;1,000&quot;</code>, <code>&quot;1,001&quot;</code>, and <code>&quot;1,002&quot;</code> each contain one comma, giving a total of 3.</p>
+</div>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">n = 998</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">0</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>All numbers from 1 to 998 have fewer than four digits. Therefore, no commas are used.</p>
+</div>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= n &lt;= 10<sup>5</sup></code></li>
+</ul>

LeetCode/4245-count-commas-in-range/solution.cpp

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+class Solution {
+public:
+    int countCommas(int n) {
+        auto commas = [](int x) {
+            string s = to_string(x);
+            return (s.size() - 1) / 3;
+        };
+        
+        int ans = 0;
+        for (int i=1; i<=n; i++) {
+            ans += commas(i);
+        }
+
+        return ans;
+    }
+};