LeetCode #384 - Shuffle an Array

最新推荐文章于 2019-01-10 17:33:31 发布

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本文介绍了一种用于将不含重复元素的数组进行随机排列的方法。通过实例演示了如何初始化数组、重置数组到初始状态以及如何对数组进行随机洗牌。采用C++实现，详细展示了洗牌算法的具体步骤。

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题目描述：

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();

实现一个给数组元素洗牌的函数，既然是洗牌必须是等概率的让数组元素随机打乱。数组洗牌的实现方法就是遍历每一个数组元素，随机地让它与它之后的元素（不包含之前的元素）交换。

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> result=v;
        for(int i=0;i<result.size();i++)
        {
            int x=rand()%(i+1);
            swap(result[i],result[x]);
        }
        return result;
    }
    
private:
    vector<int> v;
};

/**
 * Your Solution object will be instantiated and called as such:
 * Solution obj = new Solution(nums);
 * vector<int> param_1 = obj.reset();
 * vector<int> param_2 = obj.shuffle();
 */