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Author: jimit105

1345-perform-string-shifts/README.md

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+<p>You are given a string <code>s</code> containing lowercase English letters, and a matrix <code>shift</code>, where <code>shift[i] = [direction<sub>i</sub>, amount<sub>i</sub>]</code>:</p>
+
+<ul>
+	<li><code>direction<sub>i</sub></code> can be <code>0</code> (for left shift) or <code>1</code> (for right shift).</li>
+	<li><code>amount<sub>i</sub></code> is the amount by which string <code>s</code> is to be shifted.</li>
+	<li>A left shift by 1 means remove the first character of <code>s</code> and append it to the end.</li>
+	<li>Similarly, a right shift by 1 means remove the last character of <code>s</code> and add it to the beginning.</li>
+</ul>
+
+<p>Return the final string after all operations.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;abc&quot;, shift = [[0,1],[1,2]]
+<strong>Output:</strong> &quot;cab&quot;
+<strong>Explanation:</strong>&nbsp;
+[0,1] means shift to left by 1. &quot;abc&quot; -&gt; &quot;bca&quot;
+[1,2] means shift to right by 2. &quot;bca&quot; -&gt; &quot;cab&quot;</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;abcdefg&quot;, shift = [[1,1],[1,1],[0,2],[1,3]]
+<strong>Output:</strong> &quot;efgabcd&quot;
+<strong>Explanation:</strong>&nbsp; 
+[1,1] means shift to right by 1. &quot;abcdefg&quot; -&gt; &quot;gabcdef&quot;
+[1,1] means shift to right by 1. &quot;gabcdef&quot; -&gt; &quot;fgabcde&quot;
+[0,2] means shift to left by 2. &quot;fgabcde&quot; -&gt; &quot;abcdefg&quot;
+[1,3] means shift to right by 3. &quot;abcdefg&quot; -&gt; &quot;efgabcd&quot;</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= s.length &lt;= 100</code></li>
+	<li><code>s</code> only contains lower case English letters.</li>
+	<li><code>1 &lt;= shift.length &lt;= 100</code></li>
+	<li><code>shift[i].length == 2</code></li>
+	<li><code>direction<sub>i</sub></code><sub> </sub>is either <code>0</code> or <code>1</code>.</li>
+	<li><code>0 &lt;= amount<sub>i</sub> &lt;= 100</code></li>
+</ul>

1345-perform-string-shifts/solution.py

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+# Approach 2: Compute Net Shift
+
+# L be the length of the string and N be the length of the shift array.
+# Time: O(N + L)
+# Space: O(L)
+
+class Solution:
+    def stringShift(self, s: str, shift: List[List[int]]) -> str:
+        # Count the number of left shifts. A right shift is a negative left shift.
+        left_shifts = 0
+
+        for direction, amount in shift:
+            if direction == 1:
+                amount = -amount
+            left_shifts += amount
+
+        # Convert back to a positive, do left shifts, and return.
+        left_shifts %= len(s)
+
+        s = s[left_shifts:] + s[:left_shifts]
+        return s
+