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Author: jimit105

3601-find-the-k-th-character-in-string-game-ii/README.md

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+<p>Alice and Bob are playing a game. Initially, Alice has a string <code>word = &quot;a&quot;</code>.</p>
+
+<p>You are given a <strong>positive</strong> integer <code>k</code>. You are also given an integer array <code>operations</code>, where <code>operations[i]</code> represents the <strong>type</strong> of the <code>i<sup>th</sup></code> operation.</p>
+
+<p>Now Bob will ask Alice to perform <strong>all</strong> operations in sequence:</p>
+
+<ul>
+	<li>If <code>operations[i] == 0</code>, <strong>append</strong> a copy of <code>word</code> to itself.</li>
+	<li>If <code>operations[i] == 1</code>, generate a new string by <strong>changing</strong> each character in <code>word</code> to its <strong>next</strong> character in the English alphabet, and <strong>append</strong> it to the <em>original</em> <code>word</code>. For example, performing the operation on <code>&quot;c&quot;</code> generates <code>&quot;cd&quot;</code> and performing the operation on <code>&quot;zb&quot;</code> generates <code>&quot;zbac&quot;</code>.</li>
+</ul>
+
+<p>Return the value of the <code>k<sup>th</sup></code> character in <code>word</code> after performing all the operations.</p>
+
+<p><strong>Note</strong> that the character <code>&#39;z&#39;</code> can be changed to <code>&#39;a&#39;</code> in the second type of operation.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">k = 5, operations = [0,0,0]</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">&quot;a&quot;</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>Initially, <code>word == &quot;a&quot;</code>. Alice performs the three operations as follows:</p>
+
+<ul>
+	<li>Appends <code>&quot;a&quot;</code> to <code>&quot;a&quot;</code>, <code>word</code> becomes <code>&quot;aa&quot;</code>.</li>
+	<li>Appends <code>&quot;aa&quot;</code> to <code>&quot;aa&quot;</code>, <code>word</code> becomes <code>&quot;aaaa&quot;</code>.</li>
+	<li>Appends <code>&quot;aaaa&quot;</code> to <code>&quot;aaaa&quot;</code>, <code>word</code> becomes <code>&quot;aaaaaaaa&quot;</code>.</li>
+</ul>
+</div>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">k = 10, operations = [0,1,0,1]</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">&quot;b&quot;</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>Initially, <code>word == &quot;a&quot;</code>. Alice performs the four operations as follows:</p>
+
+<ul>
+	<li>Appends <code>&quot;a&quot;</code> to <code>&quot;a&quot;</code>, <code>word</code> becomes <code>&quot;aa&quot;</code>.</li>
+	<li>Appends <code>&quot;bb&quot;</code> to <code>&quot;aa&quot;</code>, <code>word</code> becomes <code>&quot;aabb&quot;</code>.</li>
+	<li>Appends <code>&quot;aabb&quot;</code> to <code>&quot;aabb&quot;</code>, <code>word</code> becomes <code>&quot;aabbaabb&quot;</code>.</li>
+	<li>Appends <code>&quot;bbccbbcc&quot;</code> to <code>&quot;aabbaabb&quot;</code>, <code>word</code> becomes <code>&quot;aabbaabbbbccbbcc&quot;</code>.</li>
+</ul>
+</div>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= k &lt;= 10<sup>14</sup></code></li>
+	<li><code>1 &lt;= operations.length &lt;= 100</code></li>
+	<li><code>operations[i]</code> is either 0 or 1.</li>
+	<li>The input is generated such that <code>word</code> has <strong>at least</strong> <code>k</code> characters after all operations.</li>
+</ul>

3601-find-the-k-th-character-in-string-game-ii/solution.py

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+class Solution:
+    def kthCharacter(self, k: int, operations: List[int]) -> str:
+        ans = 0
+        while k != 1:
+            t = k.bit_length() - 1
+            if (1 << t) == k:
+                t -= 1
+            k -= 1 << t
+            if operations[t]:
+                ans += 1
+        return chr(ord("a") + (ans % 26))