Sync LeetCode submission Runtime - 35 ms (90.85%), Memory - 20 MB (71.43%)

Author: jimit105

0072-edit-distance/README.md

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+<p>Given two strings <code>word1</code> and <code>word2</code>, return <em>the minimum number of operations required to convert <code>word1</code> to <code>word2</code></em>.</p>
+
+<p>You have the following three operations permitted on a word:</p>
+
+<ul>
+	<li>Insert a character</li>
+	<li>Delete a character</li>
+	<li>Replace a character</li>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> word1 = &quot;horse&quot;, word2 = &quot;ros&quot;
+<strong>Output:</strong> 3
+<strong>Explanation:</strong> 
+horse -&gt; rorse (replace &#39;h&#39; with &#39;r&#39;)
+rorse -&gt; rose (remove &#39;r&#39;)
+rose -&gt; ros (remove &#39;e&#39;)
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> word1 = &quot;intention&quot;, word2 = &quot;execution&quot;
+<strong>Output:</strong> 5
+<strong>Explanation:</strong> 
+intention -&gt; inention (remove &#39;t&#39;)
+inention -&gt; enention (replace &#39;i&#39; with &#39;e&#39;)
+enention -&gt; exention (replace &#39;n&#39; with &#39;x&#39;)
+exention -&gt; exection (replace &#39;n&#39; with &#39;c&#39;)
+exection -&gt; execution (insert &#39;u&#39;)
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>0 &lt;= word1.length, word2.length &lt;= 500</code></li>
+	<li><code>word1</code> and <code>word2</code> consist of lowercase English letters.</li>
+</ul>

0072-edit-distance/solution.py

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+# Approach 2: Memoization: Top-Down Dynamic Programming
+
+# M = len(word1), N = len(word2)
+# Time: O(M * N)
+# Space: O(M * N)
+
+class Solution:
+    def minDistance(self, word1: str, word2: str) -> int:
+        memo = [
+            [None for _ in range(len(word2) + 1)] for _ in range(len(word1) + 1)
+        ]
+
+        def minDistanceRecur(word1, word2, word1_idx, word2_idx):
+            if word1_idx == 0:
+                return word2_idx
+            if word2_idx == 0:
+                return word1_idx
+            if memo[word1_idx][word2_idx] is not None:
+                return memo[word1_idx][word2_idx]
+
+            minEditDistance = 0
+            if word1[word1_idx - 1] == word2[word2_idx - 1]:
+                minEditDistance = minDistanceRecur(word1, word2, word1_idx - 1, word2_idx - 1)
+            else:
+                insert_operation = minDistanceRecur(word1, word2, word1_idx, word2_idx - 1)
+                delete_operation = minDistanceRecur(word1, word2, word1_idx - 1, word2_idx)
+                replace_operation = minDistanceRecur(word1, word2, word1_idx - 1, word2_idx - 1)
+                minEditDistance = min(insert_operation, delete_operation, replace_operation) + 1
+
+            memo[word1_idx][word2_idx] = minEditDistance
+            return minEditDistance
+
+        return minDistanceRecur(word1, word2, len(word1), len(word2))
+