LeetCode-面试题03. 数组中重复的数字-Java

public int findRepeatNumber(int[] nums) {
		int res = -1;
		Set<Integer> set = new HashSet<Integer>();
		int len = nums == null ? 0 : nums.length;
		for(int i=0;i<len;i++) {
			if(!set.add(nums[i])) {
				res=nums[i];
				break;
			}
		}
		return res;
	}