int num[1005];
class Solution {
public:
    int duplicateInArray(vector<int>& nums) {
        memset(num,0,sizeof(num));
        int len = nums.size(),now = 0,flag = 0;
        for(int i = 0;i < len;i ++) 
        {
            int j = nums[i];
            if(nums[i] < 0 || nums[i] >= len) return -1;
            if(num[j] && !flag) now = j,flag = 1;
            else num[j] ++;
        }
        if(flag) return now;
        else return -1;
    }
};