Question

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.

You may assume that the array is non-empty and the majority element always exist in the array.

Example 1:

Input: [3,2,3] Output: 3

Example 2:

Input: [2,2,1,1,1,2,2] Output: 2

Difficulty:Easy

Category:Array

Analyze

Solution

class Solution {
 public:
  int majorityElement(vector<int>& nums) {
    std::unordered_map<int, int> counts;
    for (int x : nums) {
      std::unordered_map<int, int>::iterator got = counts.find(x);
      if (got == counts.end())
        counts.insert({x, 1});
      else
        got->second++;
    }

    for (auto& x : counts) {
      if (x.second > nums.size() / 2) return x.first;
    }
    return 0;
  }
};