LeetCode 0398 - Random Pick Index

Reck Zhang

发布于 2021-08-11 11:08:02

1940

发布于 2021-08-11 11:08:02

文章被收录于专栏：Reck Zhang

Random Pick Index

Desicription

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);

Solution

class Solution {
private:
    std::map<int, std::vector<int>> map = std::map<int, std::vector<int>>{};
public:
    Solution(const std::vector<int>& nums) {
        for(int i = 0;i < nums.size(); i++) {
            map[nums[i]].push_back(i);
        }
    }

    int pick(int target) {
        auto it = map.find(target);
        if(it == map.end()) {
            return 0;
        }
        return (*it).second[rand() % (*it).second.size()];
    }
};

/**
 * Your Solution object will be instantiated and called as such:
 * Solution* obj = new Solution(nums);
 * int param_1 = obj->pick(target);
 */

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原始发表：2019-09-30，如有侵权请联系 cloudcommunity@tencent.com 删除

duplicates