出處: https://leetcode.com/explore/interview/card/top-interview-questions-easy/98/design/670/
Given an integer array nums
, design an algorithm to randomly shuffle the array. All permutations of the array should be equally likely as a result of the shuffling.
Implement the Solution
class:
Solution(int[] nums)
Initializes the object with the integer arraynums
.int[] reset()
Resets the array to its original configuration and returns it.int[] shuffle()
Returns a random shuffling of the array.
Example 1:
Input ["Solution", "shuffle", "reset", "shuffle"] [[[1, 2, 3]], [], [], []] Output [null, [3, 1, 2], [1, 2, 3], [1, 3, 2]] Explanation 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]
Constraints:
1 <= nums.length <= 200
-106 <= nums[i] <= 106
- All the elements of
nums
are unique. - At most
5 * 104
calls in total will be made toreset
andshuffle
.
/** * @param {number[]} nums */ var Solution = function(nums) { this.nums = [...nums] }; /** * @return {number[]} */ Solution.prototype.reset = function() { return this.nums }; /** * @return {number[]} */ Solution.prototype.shuffle = function() { let nums = [...this.nums] for (let i = nums.length - 1; i > 0; i--) { const j = Math.floor(Math.random() * (i + 1)) const temp = [nums[i], nums[j]] nums[i] = temp[1] nums[j] = temp[0] } return nums }; /** * Your Solution object will be instantiated and called as such: * var obj = new Solution(nums) * var param_1 = obj.reset() * var param_2 = obj.shuffle() */
這題其實有點像在考, this 在不同的作用域代表的意義。
常用技巧 : 取得 0 ~ n 之間的亂數整數
// 假設 n = 2 可能的結果是 0, 1, 2 const random = Math.floor(Math.random() * (n + 1))