"Leetcode" Shuffle an Array

Title Link: https://leetcode.com/problems/shuffle-an-array/

Topic:

Shuffle a set of numbers without duplicates.

Example:

Init an array with set 1, 2, and 3.int[] Nums = {n/a}; Solution solution = new solution (nums);//Shuffle the array [] and return its result. Any permutation of [must]-equally likely to be returned.solution.shuffle ();//Resets the array back to its original Configuration [1,2,3].solution.reset ();//Returns The random shuffling of array [1,2,3].solution.shuffle ();

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Ideas:

Using the data structure implemented in http://blog.csdn.net/yeqiuzs/article/details/52141124, each time shuffle gets the initial set of a random number and deletes it until the collection is empty, once the shuffle is completed, After completion, you need to restore the data structure of the storage collection. Time complexity Shuffle method O (n), reset method O (n), construction method O (N).

Algorithm:

public class Solution {Randomizedset rm;int nums[]; Public solution (int[] nums) {rm = new Randomizedset (); this.nums = nums;for (int i=0;i<nums.length;i++) {Rm.inse    RT (Nums[i]);} }/** resets the array to its original configuration and return it. */public int[] Reset () {rm = new Randomizedset (); for (int i=0;i<nums.length;i++) {Rm.insert (nums[i]);} return nums;} /** Returns A random shuffling of the array. */public int[] Shuffle () {randomizedset tmp = new Randomizedset (); int[] res = new Int[rm.vals.size ()];for (int i = 0; I &l T Res.length; i++) {Res[i] = Rm.getrandom (); Rm.remove (Res[i]); Tmp.insert (Res[i]);} RM = Tmp;return Res;} Class Randomizedset {/** Initialize your data structure here. */public Randomizedset () {}list<integer> vals = new Ar Raylist<integer> (); Map<integer, integer> val2idx = new Hashmap<integer, integer> ();/** * Inserts a value to the set. Returns true if the set did not already * contain the specified element. */public BoOlean Insert (int val) {if (Val2idx.containskey (val)) {return false;} else {Val2idx.put (val, Val2idx.size ()); Vals.add ( val); return true;}} /** * Removes a value from the set. Returns true if the set contained the * specified element. */public boolean remove (int val) {if (!val2idx.containskey (val)) {return false;} else {int idx = Val2idx.remove (val); if (i DX < Vals.size ()-1) {//delete the last element of the list//swap the end element and the deleted element Vals.set (idx, Vals.get (Vals.size ()-1)); Val2idx.put (Vals.get ( Vals.size ()-1), IDX);} Vals.remove (Vals.size ()-1); return true;}} /** Get a random element from the set. */random r = new Random ();p ublic int getrandom () {return Vals.get (R.nextint (Vals.size ()));}}

"Leetcode" Shuffle an Array