169. Majority Element

• Difficulty: Easy

• Topics: Array, Divide and Conquer, Bit Manipulation

• Similar Questions:

  • Majority Element II

  • Check If a Number Is Majority Element in a Sorted Array

Problem:

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

Solutions:

class Solution {
public:
    int majorityElement(vector<int>& nums) {
        if (nums.size() == 0)   return -1;
        int count = 0;
        int majority = nums[0];
        for (auto num : nums) {
            if (num == majority) {
                ++count;
            } else {
                if (--count == 0) {
                    majority = num;
                    count = 1;
                }
            }
        }

        return majority;
    }
};