961. 重复 N 次的元素

输入：[1,2,3,3]
输出：3

输入：[2,1,2,5,3,2]
输出：2

输入：[5,1,5,2,5,3,5,4]
输出：5

func repeatedNTimes(A []int) int {
	var n = len(A) / 2
	var hash = make(map[int]int)
	for _, x := range A {
		hash[x]++
	}
	for k,v := range hash {
		if v == n {
			return k
		}
	}
	return 0
}