LeetCode——Single Number

Description：

Given an array of integers, every element appears twice except for one. Find that single one.

找出只出现一次的数。

public class Solution {
    public int singleNumber(int[] nums) {
        Map<Integer, Integer> map = new HashMap<Integer, Integer>();
        
        for(int i=0; i<nums.length; i++) {
            if(map.containsKey(nums[i])) {
                int times = map.get(nums[i]);
                map.put(nums[i], times+1);
            }
            else
                map.put(nums[i], 1);
        }
        Set<Integer> set = map.keySet();
        for(int i : set) {
            if(map.get(i) == 1) {
                return i;
            }
        }
        return 0;
        
    }
}