[LeetCode] 384. Shuffle an Array 数组洗牌

Shuffle a set of numbers without duplicates.

Example:

// Init an array with set 1, 2, and 3.
int[] nums = {1,2,3};
Solution solution = new Solution(nums);

// Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] 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();

给一个没有重复数字的数组，实现重置和洗牌的功能。

解法：遍历数组每个位置，每次都随机生成一个坐标位置，然后交换当前位置和随机位置的数字，这样如果数组有n个数字，那么也随机交换了n组位置，从而达到了洗牌的目的。

Java:

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import java.util.Random;   public class Solution {     private int[] nums;     private Random random;       public Solution(int[] nums) {         this.nums = nums;         random = new Random();     }           /** Resets the array to its original configuration and return it. */     public int[] reset() {         return nums;     }           /** Returns a random shuffling of the array. */     public int[] shuffle() {         if(nums == null) return null;         int[] a = nums.clone();         for(int j = 1; j < a.length; j++) {             int i = random.nextInt(j + 1);             swap(a, i, j);         }         return a;     }           private void swap(int[] a, int i, int j) {         int t = a[i];         a[i] = a[j];         a[j] = t;     } }

Python:

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import random     class Solution(object):       def __init__(self, nums):         """         :type nums: List[int]         :type size: int         """         self.__nums = nums         def reset(self):         """         Resets the array to its original configuration and return it.         :rtype: List[int]         """         return self.__nums         def shuffle(self):         """         Returns a random shuffling of the array.         :rtype: List[int]         """         nums = list(self.__nums)         for i in xrange(len(nums)):             j = random.randint(i, len(nums)-1)             nums[i], nums[j] = nums[j], nums[i]         return nums     # Your Solution object will be instantiated and called as such: # obj = Solution(nums) # param_1 = obj.reset() # param_2 = obj.shuffle()

C++:

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class Solution { public:     Solution(vector<int> nums): v(nums) {}           /** Resets the array to its original configuration and return it. */     vector<int> reset() {         return v;     }           /** Returns a random shuffling of the array. */     vector<int> shuffle() {         vector<int> res = v;         for (int i = 0; i < res.size(); ++i) {             int t = i + rand() % (res.size() - i);             swap(res[i], res[t]);         }         return res;     }       private:     vector<int> v; };

　　

 

 

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