169. Majority Element

題目原文

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

解題思路

1. 將nums掃描一次，統計哪些數字出現幾次。

2. 最後可以知道誰大於n / 2。

程式解答

class Solution 
{
public:
    int majorityElement(vector<int>& nums) 
    {
        int n = nums.size() / 2;
        map<int, int> p;
        
        for (auto i : nums)
        {
            p[i]++;
        
            if (p[i] > n)
                return i;
        }
    }
};