[Leetcode 229, Medium] Majority Element II

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Problem:

Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. The algorithm should run in linear time and in O(1) space.

Analysis:

Use Boyer-Moore voting algorithm (https://en.wikipedia.org/wiki/Boyer%E2%80%93Moore_majority_vote_algorithm ) , and then test the candidate elements are eligible for majority elements.

Solutions:

C++:

    vector<int> majorityElement(vector<int>& nums) {        vector<int> results;        if(nums.empty())            return results;                    if(nums.size() == 1) {            results.push_back(nums[0]);            return results;        }        int first = 0, second = 0, f_count = 0, s_count = 0;        for(int i = 0; i < nums.size(); ++i) {            if(f_count == 0) {                first = nums[i];                ++f_count;            } else if(nums[i] == first) {                ++f_count;            }else if(s_count == 0) {                second = nums[i];                ++s_count;            } else if(nums[i] == second) {                ++s_count;            } else {                --f_count;                --s_count;            }        }                f_count = 0;        s_count = 0;        for(int i = 0; i < nums.size(); ++i) {            if(nums[i] == first)                ++f_count;            else if(nums[i] == second)                ++s_count;        }                if(f_count > nums.size() / 3)            results.push_back(first);                    if(s_count > nums.size() / 3)            results.push_back(second);    }

Java:

Python:

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