Sync LeetCode submission Runtime - 0 ms (100.00%), Memory - 17.9 MB (6.74%)

Author: jimit105

0670-maximum-swap/README.md

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+<p>You are given an integer <code>num</code>. You can swap two digits at most once to get the maximum valued number.</p>
+
+<p>Return <em>the maximum valued number you can get</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> num = 2736
+<strong>Output:</strong> 7236
+<strong>Explanation:</strong> Swap the number 2 and the number 7.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> num = 9973
+<strong>Output:</strong> 9973
+<strong>Explanation:</strong> No swap.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>0 &lt;= num &lt;= 10<sup>8</sup></code></li>
+</ul>

0670-maximum-swap/solution.py

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+# Time: O(n)
+# Space: O(n)
+
+"""
+Algorithm:
+1. Convert the input number to a list of digits for easier manipulation.
+2. Create a dictionary that stores the last position of each digit in the number.
+3. For each position from left to right:
+    a. Look for a larger digit (from 9 down to current digit) that appears later in the number
+    b. If found, swap these digits and return the result
+4. If no swap is needed (number is already maximum), return the original number.
+"""
+
+class Solution:
+    def maximumSwap(self, num: int) -> int:
+        digits = list(str(num))
+        n = len(digits)
+
+        last_pos = {int(digit) : i for i, digit in enumerate(digits)}
+
+        for i in range(n):
+            current_digit = int(digits[i])
+
+            for d in range(9, current_digit, -1):
+                if d in last_pos and last_pos[d] > i:
+                    digits[i], digits[last_pos[d]] = digits[last_pos[d]], digits[i]
+                    return int(''.join(digits))
+
+        return num
+
+