Majority Number III

Description:

Given an array of integers and a number k, the majority number is the number that occurs more than 1/k of the size of the array.

Find it.

Example

Given [3,1,2,3,2,3,3,4,4,4] and k=3, return 3.

Note

There is only one majority number in the array.

Challenge

O(n) time and O(k) extra space

Solution:

class Solution {
public:
	/**
	 * @param nums: A list of integers
	 * @param k: As described
	 * @return: The majority number
	 */
	int majorityNumber(vector<int> nums, int k) {
		// write your code here
		auto sz = (int)nums.size();
		unordered_map<int, int> cache;
		for (int i = 0; i < sz; ++i) {
			auto tmp = nums[i];
			if (cache.find(tmp) != cache.end())
				++cache[tmp];
			else if (cache.size() < k)
				cache[tmp] = 1;
			else {
				vector<int> gc;
				for (auto& e : cache)
					if (--e.second == 0)
					gc.push_back(e.first);
				for (auto e : gc) cache.erase(e);
			}
		}
		int rc = 0, maxn = 0;
		for (auto& e : cache) {
			if (e.second > maxn) {
				maxn = e.second;
				rc = e.first;
			}
		}
		return rc;
	}
};