不修改数组找出重复的数字

class Solution {
public:
    int duplicateInArray(vector<int>& nums) {
        int n, a[10000], h = -1;
        n = nums.size();
        for(int i = 0; i < n; i++){
            a[nums[i]]++;
            if(a[nums[i]] == 2){
                h = nums[i];
            }
        }   
        if(h != -1){
            return h;
        }
        return -1;
    }
};