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leetcode/problem/shuffle-an-array.html

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+<p>Given an integer array <code>nums</code>, design an algorithm to randomly shuffle the array. All permutations of the array should be <strong>equally likely</strong> as a result of the shuffling.</p>
+
+<p>Implement the <code>Solution</code> class:</p>
+
+<ul>
+	<li><code>Solution(int[] nums)</code> Initializes the object with the integer array <code>nums</code>.</li>
+	<li><code>int[] reset()</code> Resets the array to its original configuration and returns it.</li>
+	<li><code>int[] shuffle()</code> Returns a random shuffling of the array.</li>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input</strong>
+[&quot;Solution&quot;, &quot;shuffle&quot;, &quot;reset&quot;, &quot;shuffle&quot;]
+[[[1, 2, 3]], [], [], []]
+<strong>Output</strong>
+[null, [3, 1, 2], [1, 2, 3], [1, 3, 2]]
+
+<strong>Explanation</strong>
+Solution solution = new Solution([1, 2, 3]);
+solution.shuffle();    // Shuffle the array [1,2,3] and return its result.
+                       // Any permutation of [1,2,3] must be equally likely to be returned.
+                       // Example: return [3, 1, 2]
+solution.reset();      // Resets the array back to its original configuration [1,2,3]. Return [1, 2, 3]
+solution.shuffle();    // Returns the random shuffling of array [1,2,3]. Example: return [1, 3, 2]
+
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= nums.length &lt;= 200</code></li>
+	<li><code>-10<sup>6</sup> &lt;= nums[i] &lt;= 10<sup>6</sup></code></li>
+	<li>All the elements of <code>nums</code> are <strong>unique</strong>.</li>
+	<li>At most <code>5 * 10<sup>4</sup></code> calls <strong>in total</strong> will be made to <code>reset</code> and <code>shuffle</code>.</li>
+</ul>