[LeetCode] 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();

 

这道题让我们给数组洗牌，也就是随机打乱顺序，那么由于之前那道题这个帖子的最后部分的概率图表，前面那种写法不是真正的随机分布，应该使用Knuth shuffle算法，感谢热心网友们的留言，参见代码如下：

 

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;
};

 

类似题目：

Linked List Random Node

 

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