Package g0401_0500.s0457_circular_array_loop

Class Solution

java.lang.Object
g0401_0500.s0457_circular_array_loop.Solution
public class Solution extends Object
457 - Circular Array Loop.<p>Medium</p> <p>You are playing a game involving a <strong>circular</strong> array of non-zero integers <code>nums</code>. Each <code>nums[i]</code> denotes the number of indices forward/backward you must move if you are located at index <code>i</code>:</p> <ul> <li>If <code>nums[i]</code> is positive, move <code>nums[i]</code> steps <strong>forward</strong> , and</li> <li>If <code>nums[i]</code> is negative, move <code>nums[i]</code> steps <strong>backward</strong>.</li> </ul> <p>Since the array is <strong>circular</strong> , you may assume that moving forward from the last element puts you on the first element, and moving backwards from the first element puts you on the last element.</p> <p>A <strong>cycle</strong> in the array consists of a sequence of indices <code>seq</code> of length <code>k</code> where:</p> <ul> <li>Following the movement rules above results in the repeating index sequence <code>seq[0] -> seq[1] -> ... -> seq[k - 1] -> seq[0] -> ...</code></li> <li>Every <code>nums[seq[j]]</code> is either <strong>all positive</strong> or <strong>all negative</strong>.</li> <li><code>k > 1</code></li> </ul> <p>Return <code>true</code> <em>if there is a <strong>cycle</strong> in</em> <code>nums</code><em>, or</em> <code>false</code> <em>otherwise</em>.</p> <p><strong>Example 1:</strong></p> <p><strong>Input:</strong> nums = [2,-1,1,2,2]</p> <p><strong>Output:</strong> true</p> <p><strong>Explanation:</strong> There is a cycle from index 0 -> 2 -> 3 -> 0 -> &hellip; The cycle&rsquo;s length is 3.</p> <p><strong>Example 2:</strong></p> <p><strong>Input:</strong> nums = [-1,2]</p> <p><strong>Output:</strong> false</p> <p><strong>Explanation:</strong> The sequence from index 1 -> 1 -> 1 -> &hellip; is not a cycle because the sequence&rsquo;s length is 1. By definition the sequence&rsquo;s length must be strictly greater than 1 to be a cycle.</p> <p><strong>Example 3:</strong></p> <p><strong>Input:</strong> nums = [-2,1,-1,-2,-2]</p> <p><strong>Output:</strong> false</p> <p><strong>Explanation:</strong> The sequence from index 1 -> 2 -> 1 -> &hellip; is not a cycle because nums[1] is positive, but nums[2] is negative. Every nums[seq[j]] must be either all positive or all negative.</p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= nums.length <= 5000</code></li> <li><code>-1000 <= nums[i] <= 1000</code></li> <li><code>nums[i] != 0</code></li> </ul> <p><strong>Follow up:</strong> Could you solve it in <code>O(n)</code> time complexity and <code>O(1)</code> extra space complexity?</p>

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • circularArrayLoop

      public boolean circularArrayLoop(int[] arr)