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Author: jimit105

3174-minimum-number-of-changes-to-make-binary-string-beautiful/README.md

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+<p>You are given a <strong>0-indexed</strong> binary string <code>s</code> having an even length.</p>
+
+<p>A string is <strong>beautiful</strong> if it&#39;s possible to partition it into one or more substrings such that:</p>
+
+<ul>
+	<li>Each substring has an <strong>even length</strong>.</li>
+	<li>Each substring contains <strong>only</strong> <code>1</code>&#39;s or <strong>only</strong> <code>0</code>&#39;s.</li>
+</ul>
+
+<p>You can change any character in <code>s</code> to <code>0</code> or <code>1</code>.</p>
+
+<p>Return <em>the <strong>minimum</strong> number of changes required to make the string </em><code>s</code> <em>beautiful</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;1001&quot;
+<strong>Output:</strong> 2
+<strong>Explanation:</strong> We change s[1] to 1 and s[3] to 0 to get string &quot;1100&quot;.
+It can be seen that the string &quot;1100&quot; is beautiful because we can partition it into &quot;11|00&quot;.
+It can be proven that 2 is the minimum number of changes needed to make the string beautiful.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;10&quot;
+<strong>Output:</strong> 1
+<strong>Explanation:</strong> We change s[1] to 1 to get string &quot;11&quot;.
+It can be seen that the string &quot;11&quot; is beautiful because we can partition it into &quot;11&quot;.
+It can be proven that 1 is the minimum number of changes needed to make the string beautiful.
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;0000&quot;
+<strong>Output:</strong> 0
+<strong>Explanation:</strong> We don&#39;t need to make any changes as the string &quot;0000&quot; is beautiful already.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>2 &lt;= s.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>s</code> has an even length.</li>
+	<li><code>s[i]</code> is either <code>&#39;0&#39;</code> or <code>&#39;1&#39;</code>.</li>
+</ul>

3174-minimum-number-of-changes-to-make-binary-string-beautiful/solution.py

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+# Approach 1: Greedy
+
+# Time: O(n)
+# Space: O(1)
+
+class Solution:
+    def minChanges(self, s: str) -> int:
+        current_char = s[0]
+
+        consecutive_count = 0
+        min_changes_reqd = 0
+
+        for char in s:
+            # If current char matches the prev sequence
+            if char == current_char:
+                consecutive_count += 1
+                continue
+
+                # If we have even count of chars, start a new seq
+            if consecutive_count % 2 == 0:
+                consecutive_count = 1
+            
+            # If odd count, change the current char
+            else:
+                consecutive_count = 0
+                min_changes_reqd += 1
+
+            # Update current char for next iteration
+            current_char = char
+
+        return min_changes_reqd
+