【leetcode】398. Random Pick Index【M】

最新推荐文章于 2021-08-30 08:44:18 发布

原创最新推荐文章于 2021-08-30 08:44:18 发布 · 1.3k 阅读

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#leetcode #leetcode题解 #python #哈希表 #shuffle

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本文介绍了一种在含重复元素的整数数组中随机选择指定目标值索引的方法。通过使用Python字典记录每个目标值的所有出现位置，再利用随机函数shuffle实现随机选择，确保每次选择的概率相同。

Given an array of integers with possible duplicates, randomly output the index of a given target number. You can assume that the given target number must exist in the array.

Note:
The array size can be very large. Solution that uses too much extra space will not pass the judge.

Example:

int[] nums = new int[] {1,2,3,3,3};
Solution solution = new Solution(nums);

// pick(3) should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning.
solution.pick(3);

// pick(1) should return 0. Since in the array only nums[0] is equal to 1.
solution.pick(1);

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帅帅说这个题很简单还是个medium

一看果然不难，主要是Python有个函数直接随机乱序，然后随便输出一个就行了

当然了，用字典散列这种数据结构还是很有必要的

代码好短看着好开心哈哈哈

class Solution(object):

    def __init__(self, nums):
        self.dic = {}
        for i in xrange(len(nums)):
            self.dic[nums[i]] = self.dic.get(nums[i],[]) + [i]


    def pick(self, target):
        res = self.dic[target]
        random.shuffle(res)
        return res[0]