Algorithm
Problem Name: 384. Shuffle an Array
Problem Link: https://leetcode.com/problems/shuffle-an-array/
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 <= 50-106 <= nums[i] <= 106- All the elements of
numsare unique. - At most
104calls in total will be made toresetandshuffle.
Code Examples
#1 Code Example with Java Programming
Code -
Java Programming
class Solution {
private int[] nums;
private Random random;
public Solution(int[] nums) {
this.nums = nums;
random = new Random();
}
public int[] reset() {
return nums;
}
public int[] shuffle() {
if (nums == null) return null;
int[] shuf = nums.clone();
for (int i=1;i < shuf.length;i++) {
int l = random.nextInt(i+1);
swap(shuf, i, l);
}
return shuf;
}
private void swap(int[] arr, int a, int b) {
int temp = arr[a];
arr[a] = arr[b];
arr[b] = temp;
}
}
Input
["Solution", "shuffle", "reset", "shuffle"]
[[[1, 2, 3]], [], [], []]
Output
[null, [3, 1, 2], [1, 2, 3], [1, 3, 2]]
#2 Code Example with Javascript Programming
Code -
Javascript Programming
const Solution = function(nums) {
this.original = nums;
};
Solution.prototype.reset = function() {
return this.original;
};
Solution.prototype.shuffle = function() {
const res = [];
const len = this.original.length;
let idx = 0;
let i = 0;
while (idx < = len - 1) {
i = Math.floor(Math.random() * len);
if (res[i] == null) {
res[i] = this.original[idx];
idx += 1;
}
}
return res;
};
Input
["Solution", "shuffle", "reset", "shuffle"]
[[[1, 2, 3]], [], [], []]
Output
[null, [3, 1, 2], [1, 2, 3], [1, 3, 2]]
#3 Code Example with Python Programming
Code -
Python Programming
class Solution:
def __init__(self, nums: List[int]):
self.arr = nums
self.org = nums[:]
def reset(self) -> List[int]:
"""
Resets the array to its original configuration and return it.
"""
self.arr = self.org[:]
return self.arr
def shuffle(self) -> List[int]:
"""
Returns a random shuffling of the array.
"""
random.shuffle(self.arr)
return self.arr
# Your Solution object will be instantiated and called as such:
# obj = Solution(nums)
# param_1 = obj.reset()
# param_2 = obj.shuffle()
Input
["Solution", "shuffle", "reset", "shuffle"]
[[[1, 2, 3]], [], [], []]
Output
[null, [3, 1, 2], [1, 2, 3], [1, 3, 2]]